Manufacturing method of semiconductor device

ABSTRACT

An insulating film and another insulating film are formed over a semiconductor substrate in that order to cover first, second, and third gate electrodes. The another insulating film is etched back to form sidewall spacers over side surfaces of the insulating film. Then, the sidewall spacers over the side surfaces of the insulating films corresponding to the sidewalls of the first and second gate electrodes are removed to leave the sidewall spacers over the side surfaces of the insulating film corresponding to the sidewalls of the third gate electrode. Then, the sidewall spacers and the insulating films are etched back, so that the sidewall spacers are formed of the insulating film over the sidewalls of the first, second, and third gate electrodes.

CROSS-REFERENCE TO RELATED APPLICATIONS

The disclosure of Japanese Patent Application No. 2012-223643 filed onOct. 5, 2012 including the specification, drawings and abstract isincorporated herein by reference in its entirety.

BACKGROUND

The present invention relates to manufacturing methods of semiconductordevices, and more specifically, to a technique that can be suitablyapplied to a manufacturing method of a semiconductor device including ametal-insulator-semiconductor field-effect transistor (MISFET).

A MISFET can be formed by depositing a gate insulating film over asemiconductor substrate, forming a gate electrode over the gateinsulating film, forming low-concentration regions for source and drainby ion implantation, and forming high-concentration regions for thesource and drain by ion implantation after forming sidewall spacers onsidewalls of the gate electrode.

Japanese Unexamined Patent Publication No. Hei 06 (1994)-181293 (PatentDocument 1) discloses a technique for making an offset length of asource/drain of a transistor for high voltage longer than that of asource/drain of a normal transistor by increasing the width of asidewall insulating film of the high-voltage transistor as compared tothat of a sidewall insulating film of the normal transistor.

Japanese Unexamined Patent Publication No. 2006-203225 (Patent Document2) discloses a technique for forming a metal silicide layer in ahigh-concentration region self-aligned with a gate sidewall layer in aMISFET for the high-speed operation, and also for forming another metalsilicide layer in another high-concentration region in contact with aLDD portion having a larger width than that of the gate sidewall layerin another MISFET for the high-voltage drive.

Japanese Unexamined Patent Publication No. 2001-93984 (Patent Document3) discloses a technique for forming a sidewall 123 and another thickersidewall 113.

RELATED ART DOCUMENTS Patent Documents [Patent Document 1]

Japanese Unexamined Patent Publication No. Hei 06 (1994)-181293

[Patent Document 2]

Japanese Unexamined Patent Publication No. 2006-203225

[Patent Document 3]

Japanese Unexamined Patent Publication No. 2001-93984

SUMMARY

A technique is proposed which forms a MISFET by forming a sidewallspacer as a sidewall insulating film over each sidewall of a gateelectrode. Such a semiconductor device, however, is still required toimprove its performance as much as possible, or to improve thereliability. Alternatively, the semiconductor device is required toachieve both features.

Other problems and new features of the present invention will be betterunderstood after a reading of the following detailed description inconnection with the accompanying drawings.

According to one embodiment of the invention, a first insulating filmand a second insulating film made of a different material from that ofthe first insulating film are formed over a semiconductor substrate inthat order to cover first and second gate electrodes. The secondinsulating film is etched back to form a first sidewall insulating filmover a first side surface of the first insulating film corresponding tothe sidewall of the first gate electrode, and to form a second sidewallinsulating film over a second side surface of the second insulating filmcorresponding to the sidewall of the second gate electrode. Then, thefirst sidewall insulating film is removed to leave the second sidewallinsulating film. The second sidewall insulating film and the firstinsulating film are etched back to form a third sidewall insulating filmmade of the first insulating film over the sidewall of the first gateelectrode, and to form a fourth sidewall insulating film made of thefirst insulating film over the sidewall of the second gate electrode.The width of the third sidewall insulating film is smaller than that ofthe fourth sidewall insulating film.

According to one embodiment of the invention, the semiconductor devicecan improve its performance, or reliability. Alternatively, thesemiconductor device can achieve both features.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart showing manufacturing steps of a semiconductordevice according to one embodiment of the invention;

FIG. 2 is another flowchart showing other manufacturing steps of thesemiconductor device in the one embodiment;

FIG. 3 is a cross-sectional view of a main part of one manufacturingstep of the semiconductor device in the one embodiment;

FIG. 4 is a cross-sectional view of a main part of another manufacturingstep of the semiconductor device, following the step shown in FIG. 3;

FIG. 5 is a cross-sectional view of a main part of another manufacturingstep of the semiconductor device, following the step shown in FIG. 4;

FIG. 6 is a cross-sectional view of a main part of another manufacturingstep of the semiconductor device, following the step shown in FIG. 5;

FIG. 7 is a cross-sectional view of a main part of another manufacturingstep of the semiconductor device, following the step shown in FIG. 6;

FIG. 8 is a cross-sectional view of a main part of another manufacturingstep of the semiconductor device, following the step shown in FIG. 7;

FIG. 9 is a cross-sectional view of a main part of another manufacturingstep of the semiconductor device, following the step shown in FIG. 8;

FIG. 10 is a cross-sectional view of a main part of anothermanufacturing step of the semiconductor device, following the step shownin FIG. 9;

FIG. 11 is a cross-sectional view of a main part of anothermanufacturing step of the semiconductor device, following the step shownin FIG. 10;

FIG. 12 is a cross-sectional view of a main part of anothermanufacturing step of the semiconductor device, following the step shownin FIG. 11;

FIG. 13 is a cross-sectional view of a main part of anothermanufacturing step of the semiconductor device, following the step shownin FIG. 12;

FIG. 14 is a cross-sectional view of a main part of anothermanufacturing step of the semiconductor device, following the step shownin FIG. 12;

FIG. 15 is a cross-sectional view of a main part of anothermanufacturing step of the semiconductor device, following the step shownin FIG. 13;

FIG. 16 is a cross-sectional view of a main part of anothermanufacturing step of the semiconductor device, following the step shownin FIG. 15;

FIG. 17 is a cross-sectional view of a main part of anothermanufacturing step of the semiconductor device, following the step shownin FIG. 16;

FIG. 18 is a cross-sectional view of a main part of anothermanufacturing step of the semiconductor device, following the step shownin FIG. 17;

FIG. 19 is a cross-sectional view of a main part of anothermanufacturing step of the semiconductor device, following the step shownin FIG. 18;

FIG. 20 is a cross-sectional view of a main part of anothermanufacturing step of the semiconductor device, following the step shownin FIG. 19;

FIG. 21 is a cross-sectional view of a main part of anothermanufacturing step of the semiconductor device, following the step shownin FIG. 20;

FIG. 22 is a cross-sectional view of a main part of anothermanufacturing step of the semiconductor device, following the step shownin FIG. 21;

FIG. 23 is a cross-sectional view of a main part of anothermanufacturing step of the semiconductor device, following the step shownin FIG. 22;

FIG. 24 is a cross-sectional view of a main part of anothermanufacturing step of the semiconductor device, following the step shownin FIG. 23;

FIG. 25 is a cross-sectional view of a main part of anothermanufacturing step of the semiconductor device, following the step shownin FIG. 24;

FIG. 26 is a cross-sectional view of a main part of anothermanufacturing step of the semiconductor device, following the step shownin FIG. 25;

FIG. 27 is a cross-sectional view of a main part of anothermanufacturing step of the semiconductor device, following the step shownin FIG. 26;

FIG. 28 is a cross-sectional view of a main part of one manufacturingstep of the semiconductor device in a first examined example;

FIG. 29 is a cross-sectional view of a main part of anothermanufacturing step of the semiconductor device in a first examinedexample, following the step shown in FIG. 28;

FIG. 30 is a cross-sectional view of a main part of anothermanufacturing step of the semiconductor device in a first examinedexample, following the step shown in FIG. 29;

FIG. 31 is a cross-sectional view of a main part of anothermanufacturing step of the semiconductor device in a first examinedexample, following the step shown in FIG. 30;

FIG. 32 is a cross-sectional view of a main part of one manufacturingstep of the semiconductor device in a second examined example;

FIG. 33 is a cross-sectional view of a main part of anothermanufacturing step of the semiconductor device in the second examinedexample, following the step shown in FIG. 32;

FIG. 34 is a cross-sectional view of a main part of anothermanufacturing step of the semiconductor device in the second examinedexample, following the step shown in FIG. 33;

FIG. 35 is a cross-sectional view of a main part of anothermanufacturing step of the semiconductor device in the second examinedexample, following the step shown in FIG. 34;

FIG. 36 is a cross-sectional view of a main part of anothermanufacturing step of the semiconductor device in the second examinedexample, following the step shown in FIG. 35;

FIG. 37 is a cross-sectional view of a main part of anothermanufacturing step of the semiconductor device in the second examinedexample, following the step shown in FIG. 36;

FIG. 38 is another flowchart showing manufacturing steps of thesemiconductor device in another embodiment;

FIG. 39 is a cross-sectional view of a main part of one manufacturingstep of the semiconductor device in the another embodiment;

FIG. 40 is a cross-sectional view of a main part of anothermanufacturing step of the semiconductor device, following the step shownin FIG. 39;

FIG. 41 is a cross-sectional view of a main part of anothermanufacturing step of the semiconductor device, following the step shownin FIG. 40;

FIG. 42 is a cross-sectional view of a main part of anothermanufacturing step of the semiconductor device, following the step shownin FIG. 41;

FIG. 43 is a cross-sectional view of a main part of anothermanufacturing step of the semiconductor device, following the step shownin FIG. 42;

FIG. 44 is a cross-sectional view of a main part of anothermanufacturing step of the semiconductor device, following the step shownin FIG. 43; and

FIG. 45 is a cross-sectional view of a main part of anothermanufacturing step of the semiconductor device, following the step shownin FIG. 44.

DETAILED DESCRIPTION

The following preferred embodiments of the invention may be describedbelow by being divided into a plurality of sections or embodiments forconvenience, if necessary, which are not independent from each otherunless otherwise specified. One of the sections or embodiments may be amodified example, a detailed description, or supplementary explanationof a part or all of the other. Even when referring to a specific numberregarding an element and the like (including the number of elements, anumerical value, an amount, a range, and the like) in the followingembodiments, the invention is not limited to the specific number, andmay take the number greater than, or less than the specific number,unless otherwise specified, and except when limited to the specificnumber in principle. The components (including elements or steps) in thefollowing embodiments are not necessarily essential unless otherwisespecified, and except when clearly considered to be essential inprinciple. Likewise, when referring to the shape of one component, orthe positional relationship between the components in the followingembodiments, any shape or positional relationship substantially similaror approximate to that described herein may be included in the inventionunless otherwise specified and except when clearly considered not to beso in principle. The same goes for the above numerical value, and therange.

Now, the preferred embodiments of the invention will be described indetail below with reference to the accompanying drawings. In eachdrawing for explaining the embodiments, the same or like parts havingthe same function are indicated by the same or similar referencecharacters, and its description will not be repeated in principle. Inthe embodiments below, the description of the same or like parts willnot be repeated in principle if not necessary.

In the accompanying drawings used in the embodiments, even somecross-sectional views may omit hatching for easy understanding. On theother hand, even some plan views may be designated by hatching for easyunderstanding.

First Embodiment Manufacturing Procedure of Semiconductor Device

A manufacturing procedure of a semiconductor device in this embodimentof the invention will be described below with reference to theaccompanying drawings. FIGS. 1 and 2 are flowcharts showingmanufacturing steps of the semiconductor device in the one embodiment;and FIGS. 3 to 27 are cross-sectional views of main parts of themanufacturing steps of the semiconductor device in this embodiment.

As shown in FIG. 3, first, a semiconductor substrate (semiconductorwafer) SUB is provided which is made of p-type monocrystal silicon andhas a specific resistance of about 1 to 10 Ωcm (in step S1 shown in FIG.1).

The semiconductor substrate SUB includes a low breakdown voltage MISFETformation region 1A in which a MISFETQ1 having a low breakdown voltageis formed, an intermediate breakdown voltage MISFET formation region 1Bin which a MISFETQ2 having an intermediate breakdown voltage is formed,and a high breakdown voltage MISFET formation region 1C in which aMISFETQ3 having a high breakdown voltage is formed. For easyunderstanding, as shown in FIG. 3, the low breakdown voltage MISFETformation region 1A, the intermediate breakdown voltage MISFET formationregion 1B, and the high intermediate breakdown voltage MISFET formationregion 1C are adjacent to each other. The positional relationship amongthe low breakdown voltage MISFET formation region 1A, the intermediatebreakdown voltage MISFET formation region 1B, and the high breakdownvoltage MISFET formation region 1C (actual positional relationship) inthe semiconductor substrate SUB can be changed if necessary.

The operation voltage of the high breakdown voltage MISFETQ3 is higherthan that of the intermediate breakdown voltage MISFETQ2. The operationvoltage of the intermediate breakdown voltage MISFETQ2 is higher thanthat of the low breakdown voltage MISFETQ1. In other words, the highbreakdown voltage MISFETQ3 is a MISFET that operates at a first powersupply voltage. The intermediate breakdown voltage MISFETQ2 is a MISFETthat operates at a second power supply voltage lower than the firstpower supply voltage. The low breakdown voltage MISFETQ1 is a MISFETthat operates at a third power supply voltage lower than the secondpower supply voltage. The first power supply voltage at which the highbreakdown voltage MISFETQ3 is operated is, for example, about 5V. Thesecond power supply voltage at which the intermediate breakdown voltageMISFETQ2 is operated is, for example, about 3V. The third power supplyvoltage at which the low breakdown voltage MISFETQ3 is operated is, forexample, about 1V. As will be described later, the thickness of a gateinsulating film of the high breakdown voltage MISFETQ3 is more than thatof a gate insulating film of the intermediate breakdown voltageMISFETQ2, and the thickness of the gate insulating film of theintermediate breakdown voltage MISFETQ2 is more than that of a gateinsulating film of the low breakdown voltage MISFETQ1.

Then, element isolation regions ST are formed of an insulator(specifically, an insulator embedded in a trench) in the main surface ofthe semiconductor substrate SUB, for example, by shallow trenchisolation (STI) method (in step S2 shown in FIG. 1).

Specifically, element isolation trenches (trench) STa are formed in themain surface of the semiconductor substrate SUB by etching or the like.Then, an insulating film is formed of silicon oxide (for example, ozonetetraethoxysilane (TEOS) oxide film) or the like over the semiconductorsubstrate SUB to fill the element isolation trench STa. The insulatingfilm is polished by chemical mechanical polishing (CMP) or the like toremove unnecessary parts of the insulating film located outside theelement isolation trenches STa, while maintaining the other part of theinsulating film located inside each trench STa. In this way, eachelement isolation region ST can be formed of the insulating film(insulator) filling the element isolation trench STa.

An active region of the semiconductor substrate SUB is defined by theelement isolation regions ST. A metal insulator semiconductor fieldeffect transistor (MISFET) Q1 is formed in the active region defined bythe element isolation regions ST in the low breakdown voltage MISFETformation region 1A as will be described later. The MISFET (metalinsulator semiconductor field effect transistor) Q2 is formed in theactive region defined by the element isolation regions ST in theintermediate breakdown voltage MISFET formation region 1B as will bedescribed later. The MISFET (metal insulator semiconductor field effecttransistor) Q3 is formed in the active region defined by the elementisolation regions ST in the high breakdown voltage MISFET formationregion 1C as will be described later.

Then, as shown in FIG. 4, n-type wells (n-type semiconductor regions)NW1, NW2, and NW3 are formed in a predetermined depth from the mainsurface of the semiconductor substrate SUB (in step S3 shown in FIG. 1).

The n-type wells NW1, NW2, and NW3 can be formed by ion-implantingn-type impurities, such as phosphorus (P) or arsenic (As), in thesemiconductor substrate SUB. The n-type well NW1 is formed in the lowbreakdown voltage MISFET formation region 1A, the n-type well NW2 isformed in the intermediate breakdown voltage MISFET formation region 1B,and the n-type well NW3 is formed in the high breakdown voltage MISFETformation region 1C.

The ion implantation for forming the n-type well NW1, the ionimplantation for forming the n-type well NW2, and the ion implantationfor forming the n-type well NW3 can be performed in the same ionimplantation step, which leads to a decrease in number of steps inmanufacturing. Alternatively, these ion implantation processes may beperformed in different steps.

Then, gate insulating films GI1, GI2, and GI3 are formed over the mainsurface of the semiconductor substrate SUB (in step S4 shown in FIG. 1).The gate insulating film GI1 is formed over the surface of thesemiconductor substrate SUB (that is, the upper surface of the n-typewell NW1) in the low breakdown voltage MISFET formation region 1A. Thegate insulating film. GI2 is formed over the surface of thesemiconductor substrate SUB (that is, the upper surface of the n-typewell NW2) in the intermediate breakdown voltage MISFET formation region1B. The gate insulating film. GI3 is formed over the surface of thesemiconductor substrate SUB (that is, the upper surface of the n-typewell NW3) in the high breakdown voltage MISFET formation region 1C.

The formation of the gate insulating films GI1, GI2, and GI3 in step S4can be performed, for example, as follows (see FIGS. 5 to 7).

First, the surface of the semiconductor substrate SUB is cleaned(washed) by wet etching, for example, using hydrofluoric acid (HF)solution. Then, as shown in FIG. 5, an insulating film IL1 is formed ofa silicon oxide film or the like over the surface of the semiconductorsubstrate SUB (including the surfaces of the n-type wells NW1, NW2, andNW3).

The insulating film IL1 is an insulating film for the gate insulatingfilm GI3 of the MISFET to be formed in the high breakdown voltage MISFETformation region 1C. The insulating film IL1 can be formed, for example,by thermal oxidation. Additionally, the insulating film IL1 can also beformed by depositing a CVD film (which is a silicon oxide film formed bythe CVD method) over the thermal oxide film formed in the thermaloxidation.

Then, the insulating film IL1 is etched using a photoresist layer (notshown) as an etching mask formed by photolithography to thereby removethe insulating film IL1 in the low breakdown voltage MISFET formationregion 1A and the intermediate breakdown voltage MISFET formation region1B, while leaving the insulating film IL1 in the high breakdown voltageMISFET formation region 1C.

Then, a silicon oxide film is formed over the main surface of thesemiconductor substrate SUB by thermal oxidation of the semiconductorsubstrate SUB. Thus, as shown in FIG. 6, an insulating film IL2 isformed of the silicon oxide film (thermal oxide film) over thesemiconductor substrate SUB (that is, over the n-type wells NW1 and NW2)in the low breakdown voltage MISFET region 1A and the intermediatebreakdown voltage MISFET formation region 1B. At the same time, theinsulating film IL1 in the high breakdown voltage MISFET formationregion 1C becomes thicker.

Then, the insulating film IL2 is etched using a photoresist layer (notshown) as an etching mask formed by the photolithography to therebyremove the insulating film IL2 in the low breakdown voltage MISFETformation region 1A while leaving the insulating film IL2 in theintermediate breakdown voltage MISFET formation region 1B and theinsulating film IL1 in the high breakdown voltage MISFET formationregion 1C.

Then, a silicon oxide film is formed over the main surface of thesemiconductor substrate SUB by thermal oxidation of the semiconductorsubstrate SUB. Thus, as shown in FIG. 7, an insulating film IL3 isformed of a silicon oxide film (thermal oxide film) over thesemiconductor substrate SUB (that is, n-type well NW1) in the lowbreakdown voltage MISFET formation region 1A. At this time, theinsulating film IL2 in the intermediate breakdown voltage MISFETformation region 1B and the insulating film IL1 in the high breakdownvoltage MISFET formation region 1C are thicker than the insulating filmIL3 in the low breakdown voltage MISFET formation region 1A.

The insulating film IL1 in the high breakdown voltage MISFET formationregion 1C increases its thickness both at the times of formation of theinsulating film IL2 and the insulating film IL3. The insulating film IL2in the intermediate breakdown voltage MISFET formation region 1Bincreases its thickness only at the time of formation of the insulatingfilm IL3. Thus, the thickness of the insulating film IL2 formed in theintermediate breakdown voltage MISFET formation region 1B is more thanthat of the insulating film IL3 formed in the low breakdown voltageMISFET formation region 1A. The thickness of the insulating film IL1formed in the high breakdown voltage MISFET formation region 1C is morethan that of the insulating film IL2 formed in the intermediatebreakdown voltage MISFET formation region 1B.

The insulating film IL3 formed in the low breakdown voltage MISFETformation region 1A is a gate insulating film GI1 for the low breakdownvoltage MISFETQ1 formed in the low breakdown voltage MISFET formationregion 1A. The insulating film IL2 formed in the intermediate breakdownvoltage MISFET formation region 1B is a gate insulating film GI2 for theintermediate breakdown voltage MISFETQ2 formed in the intermediatebreakdown voltage MISFET formation region 1B. The insulating film IL1formed in the high breakdown voltage MISFET formation region 1C is agate insulating film GI3 for the high breakdown voltage MISFETQ3 formedin the high breakdown voltage MISFET formation region 1C.

In this way, the gate insulating films GI1, GI2, and GI3 are formed inthe step S4. The gate insulating film. GI1 is formed over the surface ofthe semiconductor substrate SUB in the low breakdown voltage MISFETformation region 1A. The gate insulating film GI2 is formed over thesurface of the semiconductor substrate SUB in the intermediate breakdownvoltage MISFET formation region 1B. The gate insulating film GI3 isformed over the surface of the semiconductor substrate SUB in the highbreakdown voltage MISFET formation region 1C.

The thickness of the gate insulating film GI2 formed in the intermediatebreakdown voltage MISFET formation region 1B is more than that of thegate insulating film GI1 formed in the low breakdown voltage MISFETformation region 1A. The thickness of the gate insulating film. GI3formed in the high breakdown voltage MISFET formation region 1C is morethan that of the gate insulating film GI2 formed in the intermediatebreakdown voltage MISFET formation region 1B. The thicknesses of thegate insulating films GI1, GI2, and GI3 are, for example, as follows.The thickness of the gate insulating film GI1 can be, for example, in arange of about 2 to 3 nm. The thickness of the gate insulating film GI2can be, for example, in a range of about 5 to 10 nm. The thickness ofthe gate insulating film GI3 can be, for example, in a range of about 10to 15 nm.

The thickness of the gate insulating film GI2 formed in the intermediatebreakdown voltage MISFET formation region 1B is more than that of thegate insulating film GI1 formed in the low breakdown voltage MISFETformation region 1A. Thus, the breakdown voltage of the MISFETQ2 formedin the intermediate breakdown voltage MISFET formation region 1B ishigher than that of the MISFETQ1 formed in the low breakdown voltageMISFET formation region 1A. The thickness of the gate insulating filmGI3 formed in the high breakdown voltage MISFET formation region 1C ismore than that of the gate insulating film GI2 formed in theintermediate breakdown voltage MISFET formation region 1B. Thus, thebreakdown voltage of the MISFETQ3 formed in the high breakdown voltageMISFET formation region 1C is higher than that of the MISFETQ2 formed inthe intermediate breakdown voltage MISFET formation region 1B.

Next, the gate electrodes GE1, GE2, and GE3 are formed (in step S5 ofFIG. 1). The formation processes of the gate electrodes GE1, GE2, andGE3 in step S5 can be performed, for example, in the following way (seeFIGS. 8 and 9).

First, as shown in FIG. 8, a conductive material film (conductive film,silicon film), such as a polycrystalline silicon film (doped polysiliconfilm) DP is formed (deposited) over the entire main surface of thesemiconductor substrate SUB (that is, over a region covering the gateinsulating films GI1, GI2, and GI3). The polycrystalline silicon film DPbecomes a semiconductor film (conductive material film) having a lowresistance formed by introducing impurities in or after the deposition.The thickness (deposited thickness) of the polycrystalline silicon filmDP can be, for example, about 180 nm. The polycrystalline silicon filmDP can be formed by converting an amorphous silicon film in thedeposition into the polycrystalline silicon film by heat treatment afterthe deposition.

Then, as shown in FIG. 9, the polycrystalline silicon film DP ispatterned by the photolithography and dry etching to thereby form thegate electrodes GE1, GE2, and GE3. The gate electrodes GE1, GE2, and GE3are respectively formed of the patterned polycrystalline silicon filmDP.

Among the gate electrodes, the gate electrode GE1 is formed over thesemiconductor substrate SUB (that is, n-type well NW1) via the gateinsulating film GI1 in the low breakdown voltage MISFET formation region1A. That is, the gate electrode GE1 is formed over the gate insulatingfilm GI1 on the surface of the semiconductor substrate SUB (n-type wellNW1) in the low breakdown voltage MISFET formation region 1A. The gateelectrode GE2 is formed over the semiconductor substrate SUB (that is,over the n-type well NW2) via the gate insulating film GI2 in theintermediate breakdown voltage MISFET formation region 1B. That is, thegate electrode GE2 is formed over the gate insulating film GI2 on thesemiconductor substrate SUB (over the n-type well NW2) in theintermediate breakdown voltage MISFET formation region 1B. The gateelectrode GE3 is formed over the semiconductor substrate SUB (that is,over the n-type well NW3) via the gate insulating film GI3 in the highbreakdown voltage MISFET formation region 1C. That is, the gateelectrode GE3 is formed over the gate insulating film. GI3 on thesurface of the semiconductor substrate SUB (n-type well NW3) in the highbreakdown voltage MISFET formation region 1C.

In this way, the gate electrodes GE1, GE2, and GE3 are formed in thestep S5.

Then, parts of the gate insulating films GI1, GI2, and GI3 not coveredwith the gate electrodes GE1, GE2, and GE3 can be removed by dry etchingfor patterning the polycrystalline silicon film DP, or by wet etchingafter the dry etching.

Although not shown in the figure, the gate electrode for an n-channelMISFET is formed of a patterned polycrystalline silicon film DP in ann-channel MISFET formation region within the low breakdown voltageMISFET formation region 1A.

In this embodiment, the gate electrodes GE1, GE2, and GE3 are formed ofa polycrystalline silicon film DP. In other embodiments, the gateelectrodes GE1, GE2, and GE3 can be formed of a metal film or metalcompound film. In this case, the gate electrodes GE1, GE2, and GE3 arethe so-called metal gate electrode.

Then, as shown in FIG. 10, p-type impurities are ion-implanted into thesemiconductor substrate SUB (n-type wells NW2 and NW3) in theintermediate breakdown voltage MISFET formation region 1B and the highbreakdown voltage MISFET formation region 1C to thereby form extensionregions (source/drain extension region, p⁻-type semiconductor region,and p-type impurity diffusion layer) EX2 and EX3 (in step S6 shown inFIG. 1). The ion implantation for forming the extension regions EX2 andEX3 performed in step S6 is hereinafter referred to as “ion implantationIM1”. FIG. 10 schematically shows the ion implantation IM1 by the arrow.

In the step S6, a photoresist layer PR 1 is formed over thesemiconductor substrate SUB in the low breakdown voltage MISFETformation region 1A so as to cover the low breakdown voltage MISFETformation region 1A and to expose the intermediate breakdown voltageMISFET formation region 1B and the high breakdown voltage MISFETformation region 1C, and then the ion implantation IM1 is performed onthe substrate SUB. Thereafter, the photoresist layer PR1 is removed. Inthe ion implantation IM1, since the low breakdown voltage MISFETformation region 1A is covered with the photoresist layer PR1, the ionimplantation is not performed on the semiconductor substrate SUB in thelow breakdown voltage MISFET formation region 1A. Thus, in the step S6,the ion implantation IM1 is performed on the semiconductor substrate SUB(n-type wells NW2 and NW3) in the intermediate breakdown voltage MISFETformation region 1B and the high breakdown voltage MISFET formationregion 1C.

In the ion implantation IM1 in step S6, the gate electrodes GE2 and GE3can act as a mask (ion implantation blocking mask) in the intermediatebreakdown voltage MISFET formation region 1B and the high breakdownvoltage MISFET formation region 1C. Thus, impurities are prevented frombeing implanted directly under the gate electrodes GE2 and GE3 over thesemiconductor substrate SUB (n-type well NW2), in the ion implantationIM1.

That is, in the intermediate breakdown voltage MISFET formation region1B, the extension region EX2 is formed in regions of the semiconductorsubstrate SUB (n-type well NW2) located on both sides of the gateelectrode GE2 by ion-implanting p-type impurities, such as boron (B).Thus, in the intermediate breakdown voltage MISFET formation region 1B,the extension region EX2 is formed to be aligned (self-aligned) witheach sidewall of the gate electrode GE2. In the high breakdown voltageMISFET formation region 1C, the extension region is formed in regions ofthe semiconductor substrate SUB (n-type well NW3) located on both sidesof the gate electrode GE3, by ion-implanting p-type impurities, such asboron (B). Thus, in the high breakdown voltage MISFET formation region1C, the extension region EX3 is formed to be aligned (self-aligned) witheach sidewall of the gate electrode GE3. In the ion implantation IM1,the p-type impurities can be ion-implanted also in the gate electrodesGE2 and GE3 (silicon films forming the electrodes).

The extension region EX2 is a semiconductor region of the sameconduction type (p-type in this embodiment) as that of the source anddrain regions SD2 to be formed later. However, the extension region EX2has a lower concentration of impurities than that of the source anddrain regions SD2, and a shallower depth (junction depth) than that ofthe source and drain regions SD2 to be formed later. The extensionregion EX3 is a semiconductor region of the same conduction type (p-typein this embodiment) as that of the source and drain regions SD3 to beformed later. However, the extension region EX3 has a lowerconcentration of impurities than that of the source and drain regionsSD3, and a shallower depth (junction depth) than that of the source anddrain regions SD3 to be formed later.

In this embodiment, the extension region EX2 in the intermediatebreakdown voltage MISFET formation region 1B, and the extension regionEX3 in the high breakdown voltage MISFET formation region 1C are formedin the same ion implantation step. In another embodiment, the extensionregion EX2 in the intermediate breakdown voltage MISFET formation region1B, and the extension region EX3 in the high breakdown voltage MISFETformation region 1C can also be formed in different ion implantationsteps.

After the ion implantation IM1, the above photoresist layer PR1 isremoved.

Then, as shown in FIG. 11, an insulating film IL4 is formed over themain surface of the semiconductor substrate SUB to cover the gateelectrodes GE1, GE2, and GE3 (in step S7 shown in FIG. 1).

The insulating film IL4 is an insulating film for an offset spacer ofthe n-channel MISFET having a low breakdown voltage. The insulating filmIL4 is formed of, for example, a silicon oxide film, and can have athickness of, for example, about 3 to 5 nm. The insulating film IL4 isformed over the upper surfaces and sidewalls of the gate electrodes GE1,GE2, and GE3, and parts of the semiconductor substrate SUB not coveredby the gate electrodes GE1, GE2, and GE3 (n-type wells NW1, NW2, andNW3). The insulating film IL4 can be formed, for example, by a chemicalvapor deposition (CVD) method and the like.

Although not shown in the figure, ion implantation (ion implantation ofn-type impurities) for formation of the n⁻-type extension region isperformed in an n-channel MISFET formation region of the low breakdownvoltage MISFET formation region 1A. At this time, a photoresist layer(not shown) is formed over the semiconductor substrate SUB to coverp-channel type MISFET formation regions of the low breakdown voltageMISFET formation region 1A, the intermediate breakdown voltage MISFETformation region 1B, and the high breakdown voltage MISFET formationregion 1C, while exposing the n-channel MISFET formation region of thelow breakdown voltage MISFET formation region 1A. After forming thephotoresist layer, ion implantation is performed. Thereafter, thephotoresist layer is removed. As a result, in the n-channel MISFETformation region of the low breakdown voltage MISFET formation region1A, n-type impurities are ion-implanted into regions of thesemiconductor substrate SUB (p-type well) on both sides of the gateelectrode for the n-channel MISFET to thereby form n⁻-type extensionregions (not shown). At this time, the gate electrode for the n-channelMISFET and the insulating film IL4 over the sidewalls thereof can serveas a mask (ion implantation blocking mask). As a result, in then-channel type MISFET formation region of the low breakdown voltageMISFET formation region 1A, the n⁻-type extension region is formed to bealigned (self-aligned) with the side surfaces of the insulating film IL4over the sidewalls of the gate electrode for the n-channel MISFET.

Then, as shown in FIG. 12, an insulating film IL5 is formed over themain surface of the semiconductor substrate SUB, that is, over theinsulating film IL4 to cover the gate electrodes GE1, GE2, and GE3 (instep S8 shown in FIG. 1).

The insulating film IL5 is an insulating film for an offset spacer ofthe p-channel MISFET having a low breakdown voltage. The insulating filmIL5 is formed of, for example, a silicon nitride film, and can have athickness of, for example, about 5 to 10 nm. The insulating film IL5 canbe formed, for example, using the CVD method or the like.

Then, as shown in FIG. 13, the insulating films IL5 and IL4 are etchedback (subjected to anisotropic etching) by a reactive ion etching (RIE)or the like to leave the insulating films IL5 and IL4 on the respectivesidewalls of the gate electrodes GE1, GE2, and GE3, while removing otherregions of the insulating films IL5 and IL4. Thus, offset spacers(sidewall insulating films) SP comprised of the remaining insulatingfilms IL5 and IL 4 are formed over sidewalls of the gate electrodes GE1,GE2, and GE3 (in step S9 shown in FIG. 1).

Referring to FIG. 13, the insulating films IL5 and IL4 are etched backto leave the insulating films IL4 and IL5 over each sidewall of the gateelectrode GE, while removing the parts of the insulating films IL5 andIL4 in other regions (over the upper surfaces of the gate electrodesGE1, GE2, and GE3, and over other parts of the semiconductor substrateSUB not covered by the gate electrodes GE1, GE2, and GE3). In this case,the offset spacer SP comprised of a lamination of the insulating filmsIL4 and IL5 is formed as the sidewall insulating film over each sidewallof the gate electrodes GE1, GE2, and GE3.

Like FIG. 13, FIG. 14 also shows another cross-sectional view of thestage after step S9. Referring to FIG. 14, the insulating film IL5located in regions except for the sidewalls of the gate electrodes GE1,GE2, and GE3 is removed in step S9 (that is, the insulating film IL5located over the upper surfaces of parts of the semiconductor substrateSUB not covered by the gate electrodes GE1, GE2, and GE3 is removed).However, the insulating film IL4 remains in the form of layer over theupper surfaces of the parts of the semiconductor substrate SUB notcovered by the gate electrodes GE1, GE2, and GE3. FIG. 13 is the same asFIG. 14 in that the insulating film IL5 located in the regions exceptfor the sidewalls of the gate electrodes GE1, GE2, and GE3 is removed instep S9. However, FIG. 13 differs from FIG. 14 in that one insulatingfilm IL4 remains in the form of layer over the upper surfaces of theparts of the semiconductor substrate SUB not covered by the gateelectrodes GE1, GE2, and GE3 (which corresponds to FIG. 14), while theother insulating film IL4 does not remain (which corresponds to FIG.13). This embodiment allows the case of FIG. 13, and also the case ofFIG. 14. Steps after the step S9 in the case of FIG. 13 are basicallythe same as those in the case of FIG. 14. For this reason, as shown inall the figures following FIG. 15, the insulating film IL4 is removedlike FIG. 13. However, also in the figures after FIG. 15, the insulatingfilm IL4 may remain in the form of layer like FIG. 14 (note that in asalicide step to be described later, the exposed insulating film IL4 canbe removed).

Then, as shown in FIG. 15, p-type impurities are ion-implanted into thesemiconductor substrate SUB (n-type well NW1) of the p-channel MISFETformation region in the low breakdown voltage MISFET formation region 1Ato thereby form extension regions (source/drain extension region,p⁻-type semiconductor region, and p-type impurity diffusion layer) EX1(in step S10 shown in FIG. 1). The ion implantation for forming theextension region EX1 is hereinafter referred to as an “ion implantationIM2”. FIG. 15 schematically shows the ion implantation IM2 by the arrow.

In step S10, a photoresist layer PR2 is formed to cover the n-channelMISFET formation region in the low breakdown voltage MISFET formationregion 1A, the intermediate breakdown voltage MISFET formation region1B, and the high breakdown voltage MISFET formation region 1C, whileexposing the p-channel MISFET formation region in the low breakdownvoltage MISFET formation region 1A. After forming the photoresist layerPR2 over the semiconductor substrate SUB, the ion implantation IM2 isperformed. Thereafter, the photoresist layer PR2 is removed. In the ionimplantation IM2, the photoresist layer PR2 covers the n-channel MISFETformation region in the low breakdown voltage MISFET formation region1A, the intermediate breakdown voltage MISFET formation region 1B, andthe high breakdown voltage MISFET formation region 1C. As a result, thesemiconductor substrate SUB within these regions are not subjected tothe ion implantation. In step S6, the ion implantation IM2 is performedin the p-channel MISFET formation region of the low breakdown voltageMISFET formation region 1A of the semiconductor substrate SUB (n-typewell NW1).

In the ion implantation IM2 in step S10, in the p-channel MISFETformation region of the low breakdown voltage MISFET formation region1A, the gate electrode GE1 and the offset spacers SP over the sidewallsthereof can serve as a mask (ion implantation blocking mask). Thus,impurities are prevented from being implanted directly under the gateelectrode GE1 and the offset spacers SP over the sidewalls thereof ofthe semiconductor substrate SUB (n-type well NW1) in performing the ionimplantation IM2. As a result, in the p-channel MISFET formation regionof the low breakdown voltage MISFET formation region 1A, p-typeimpurities, such as boron (B), are ion-implanted in regions located onboth sides of the gate electrode GE1 and the offset spacers SP over thesidewalls thereof of the semiconductor substrate SUB (n-type well NW1)to thereby form the extension regions EX1. Thus, in the low breakdownvoltage MISFET formation region 1A, the extension region EX1 is formedto be aligned (self-aligned) with the side surfaces of the offset spacerSP over the sidewalls of the gate electrode GE1. In the ion implantationIM2, the p-type impurities can be ion-implanted also in the gateelectrode GE1 (silicon film forming the electrode).

The extension region EX1 is a semiconductor region of the sameconduction type (p-type in this embodiment) as that of the source anddrain regions SD1 to be formed later. However, the extension region EX1has a lower concentration of impurities than that of the source anddrain regions SD1, and a shallower depth (junction depth) than that ofthe source and drain regions SD1 to be formed later.

After the ion implantation IM2, the above photoresist layer PR2 isremoved.

In this embodiment, in order to form the extension regions (EX1 or thelike) of the low breakdown voltage MISFET, the offset spacers are formedover the sidewalls of the gate electrode (GE1 or the like). When inother embodiments, the offset spacer does not need to be formed on thesidewall of the gate electrode (GE1 or the like) in forming theextension region (EX1 and the like), the step S7 (formation of theinsulating film IL4), the step S8 (formation of the insulating filmIL5), and the step S9 (etching back of the insulating films IL5 and IL4)can also be omitted.

Then, as shown in FIG. 16, an insulating film IL6 is formed over themain surface of the semiconductor substrate SUB to cover the gateelectrodes GE1, GE2, and GE3 and the offset spacers SP over thesidewalls thereof (in step S11 shown in FIG. 2).

The insulating film IL6 is an insulating film for a sidewall spacer SW2to be formed on the sidewalls of the gate electrodes GE1, GE2, and GE3,and preferably a single layer of the insulating film. The insulatingfilm IL6 is preferably a silicon oxide film or silicon nitride film, andfurther preferably a silicon nitride film. The formation thickness T3(deposited thickness) of the formed insulating film IL6 can be, forexample, in a range of about 30 to 50 nm. The formation thickness T3 ofthe insulating film IL6 is set taking into consideration the widths (T1a, T1 b) of wall spacers SW2 a and SW2 b to be formed later. Theinsulating film IL6 can be formed, for example, using the CVD method orthe like.

Then, as shown in FIG. 17, an insulating film IL7 is formed over themain surface of the semiconductor substrate SUB, that is, over theinsulating film IL6 (in step S12 shown in FIG. 2).

The insulating film IL7 is an insulating film for controlling the widthof the sidewall spacer SW2 to be formed later over the sidewalls of thegate electrodes GE1, GE2, and GE3. The insulating film IL7 is preferablya single layer of an insulating film, and made of material differentfrom the insulating film IL6. When the insulating film IL6 is a siliconnitride film, the insulating film IL7 is preferably a silicon oxidefilm. When the insulating film IL6 is a silicon oxide film, theinsulating film IL7 is preferably a silicon nitride film. The formationthickness T4 of the insulating film IL7 formed in step S12 is preferablysmaller (thinner) than the formation thickness T3 of the insulating filmIL6 formed in step S11. The formation thickness (deposited thickness) T4of the insulating film IL7 can be, for example, in a range of about 10to 30 nm. The formation thickness T4 of the insulating film IL7 is settaking into consideration a difference between the width (T1 c) of thesidewall spacer SW2 c and the widths (T1 a, and T1 b) of the sidewallspacers SW2 a and SW2 b which are to be formed later. The insulatingfilm IL7 can be formed, for example, using the CVD method or the like.

After the steps S11 and S12, a lamination of the insulating film IL6 andthe insulating film IL7 over the insulating film IL6 is formed over thesemiconductor substrate SUB to cover the gate electrodes GE1, GE2, andGE3 and the offset spacers SP over the sidewalls thereof.

Then, as shown in FIG. 18, the insulating film IL7 is etched back by ananisotropic etching technique (etching, dry etching, anisotropicetching) to thereby form sidewall spacers (sidewalls, sidewallinsulating films) SW1 as the sidewall insulating film over the sidesurfaces (sidewalls) IL6 a of the insulating films IL6 (in step S13shown in FIG. 2).

The side surface IL6 a of the insulating film IL6 is a side surfaceamong the surfaces of the insulating films IL6 corresponding to eachsidewall of the gate electrodes GE1, GE2, and GE3.

Since the insulating film IL6 is formed over the semiconductor substrateSUB to cover the gate electrodes GE1, GE2, and GE3 in step S11, theinsulating film IL6 is formed to reflect concavities and convexities ofthe underlayer and to conform with the gate electrodes GE1, GE2, andGE3. Thus, the insulating film IL6 is provided with the side surfaces(sidewalls) IL6 a corresponding to the sidewalls of the gate electrodesGE1, GE2, and GE3. That is, parts of the insulating film IL6 coveringthe gate electrodes GE1, GE2, and GE3 have their surface formed in aconvex shape with the side of each convex shaped part being the sidesurface IL6 a corresponding to each sidewall of the gate electrodes GE1,GE2, and GE3. The side surface IL6 a of the insulating film IL6 isformed in the position away from each sidewall of the gate electrodesGE1, GE2, and GE3 in the gate length direction by the thickness of theinsulating film IL6 (the sum of the thickness of the insulating film IL6and the thickness of the offset spacer SP in forming the offset spacerSP). The side surface IL6 a of the insulating film IL6 is usuallyparallel to each sidewall of the corresponding gate electrode GE1, GE2,or GE3. In some cases, the top of the side surface IL6 a may be rounded.

After the step S13, each sidewall spacer SW1 is formed over the sidesurface IL6 a of the insulating film IL6. From another perspective, thesidewall spacer SW1 is formed over each sidewall of the gate electrodesGE1, GE2, and GE3 via the insulating film IL6 (via the offset spacer SPand insulating film. IL6 in formation of the offset spacer SP).

In step S13, a part of the insulating film IL7 located over the sidesurface IL6 a of the insulating film IL6 is left as the sidewall spacerSW1, and the remaining part of the insulating film IL7 in the otherregion is removed. Thus, after the step S13, the parts of the insulatingfilms IL7 locally remaining over the side surface IL6 a of theinsulating film. IL6 serve as the sidewall spacer SW1, and theinsulating films IL6 except for the parts thereof covered by thesidewall spacers SW1 are exposed.

The sidewall spacer SW1 formed over the side surface IL6 a of theinsulating film IL6 corresponding to the sidewall of the gate electrodeGE1 in the low breakdown voltage MISFET formation region 1A ishereinafter referred to as a “sidewall spacer SW1 a”. The sidewallspacer SW1 formed over the side surface IL6 a of the insulating film IL6corresponding to the sidewall of the gate electrode GE2 in theintermediate breakdown voltage MISFET formation region 1B is hereinafterreferred to as a “sidewall spacer SW1 b”. The sidewall spacer SW1 formedover the side surface IL6 a of the insulating film IL6 corresponding tothe sidewall of the gate electrode GE3 in the high breakdown voltageMISFET formation region 1C is hereinafter referred to as a “sidewallspacer SW1 c”.

In step S13, the etching back is preferably performed under conditions(etching conditions) that make an etching rate of the insulating filmIL7 larger (higher) than that of the insulating film IL6. In otherwords, in step S13, the etching back is preferably performed underconditions (etching conditions) that make an etching rate of theinsulating film IL6 smaller (lower) than that of the insulating filmIL7. That is, the etching back is preferably performed on the etchingconditions in which the insulating film IL6 is less likely to be etchedthan the insulating film IL7. Thus, in step S13, the insulating film IL6can serve as an etching stopper. In step S13, the insulating film IL6can be suppressed or prevented from being etched.

In step S13, the etching rates of the insulating film IL6 and theinsulating film IL7 need to differ from each other. Also in thefollowing step S14, the etching rate of the insulating film IL6 shouldbe different from that of the insulating film IL7 (sidewall spacer SW1).Thus, the insulating film IL6 and the insulating film IL7 are formed ofdifferent materials.

In the step S13 and step S14 to be described later, the etchingconditions that can etch the insulating film IL7, while suppressingetching of the insulating film IL6 as much as possible are preferablyadopted. Thus, the material of the insulating film IL7 is preferablyselected that can have a high etching selectivity as compared to thematerial of the insulating film IL6. From this point, preferably, one ofthe insulating film IL6 and the insulating film IL7 is formed of asilicon oxide film, whereas the other of the insulating film IL6 and theinsulating film IL7 is formed of a silicon nitride film.

When the insulating film IL7 is the silicon oxide film and theinsulating film IL6 is the silicon nitride film, the etching backprocess of the insulating film IL7 in step S13 preferably uses anetching gas described below by way of example. That is, for example, theetching gas for use can be a mixed gas of C₄F₈ gas, O₂ gas, and Ar gas.

Next, the sidewall spacers SW1 (that is, sidewall spacers SW1 a and SW1b) in the low breakdown voltage MISFET formation region 1A and theintermediate breakdown voltage MISFET formation region 1B are removed,and the sidewall spacer SW1 (that is, sidewall spacer SW1 c) in the highbreakdown voltage MISFET formation region 1C is maintained (in step S14shown in FIG. 2).

The process in step S14 can be performed in the following way. That is,as shown in FIG. 19, a photoresist layer (mask layer) PR3 is formed overthe semiconductor substrate SUB to cover the high breakdown voltageMISFET formation region 1C and to expose the low breakdown voltageMISFET formation region 1A and the intermediate breakdown voltage MISFETformation region 1B. Then, the sidewall spacers SW1 (that is, thesidewall spacers SW1 a and SW1 b) formed in the low breakdown voltageMISFET formation region 1A and the intermediate breakdown voltage MISFETformation region 1B are removed by the etching. Thereafter, as shown inFIG. 20, the photoresist layer PR3 is removed. In this way, the processin the step S14 is performed to remove the sidewall spacers SW1 a andSW1 b in the low breakdown voltage MISFET formation region 1A and theintermediate breakdown voltage MISFET formation region 1B.

Specifically, in the step S14, the etching is performed while thesidewall spacers SW1 (SW1 a and SW1 b) in the low breakdown voltageMISFET formation region 1A and the intermediate breakdown voltage MISFETformation region 1B are exposed, and the sidewall spacer SW1 (sidewallspacer SW1 c) in the high breakdown voltage MISFET formation region 1Cis not exposed (that is, is covered with the photoresist layer PR3). Inthe etching process in step S14, the sidewall spacers SW1 (SW1 a and SW1b) in the low breakdown voltage MISFET formation region 1A and theintermediate breakdown voltage MISFET formation region 1B are removed,and the sidewall spacer SW1 (sidewall spacer SW1 c) in the highbreakdown voltage MISFET formation region 1C remains without beingremoved.

In step S14, the etching is preferably performed under conditions(etching conditions) that makes an etching rate of the sidewall spacerSW1 larger (higher) than that of the insulating film IL6. In otherwords, in step S14, the etching is preferably performed under conditions(etching conditions) that makes an etching rate of the insulating filmIL6 smaller (lower) than that of the sidewall spacer SW1. That is, instep S14, the etching is preferably performed on the etching conditionsin which the insulating film IL6 is less likely to be etched than thesidewall spacer SW1. In step S14, the insulating film IL6 can besuppressed or prevented from being etched.

In step S14, the sidewall spacers SW1 a and SW1 b are desirably removedwhile suppressing the etching of the insulating film IL6 as much aspossible. This arrangement can suppress or prevent the decrease inthickness of the insulating film IL6 in the low breakdown voltage MISFETformation region 1A and the intermediate breakdown voltage MISFETformation region 1B by the etching in step S14, which can also suppressor prevent a difference in thickness of the insulating film IL6 betweenthe low and intermediate breakdown voltage MISFET formation regions 1Aand 1B and the high breakdown voltage MISFET formation region 1C. Fromthis point, the etching in step S14 is preferably wet etching, which canaccurately remove the sidewall spacers SW1 a and SW1 b, whilesuppressing the etching of the insulating film IL6 as much as possible.The use of wet etching can easily achieve the etching having a highetching selectivity between the silicon oxide film and the siliconnitride film. As mentioned above, preferably, one of the insulating filmIL6 and the insulating film IL7 is the silicon oxide film, while theother is the silicon nitride film, and wet etching is used as theetching in step S14. When the insulating film IL6 is the silicon nitridefilm, and the insulating film IL7 is the silicon oxide film, in stepS14, the wet etching using, for example, hydrofluoric acid (bufferedhydrofluoric acid) can be suitably used.

In the above step S13, the anisotropic etching is needed to enable theformation of the sidewall spacers SW1 and thus the dry etching isperformed. In step S15 to be described later, the anisotropic etching(also causing side etching) is needed to enable the formation of thesidewall spacers SW2, and thus the dry etching is performed. In stepS14, isotropic etching is preferable so as to remove the entire sidewallspacers SW1 a and SW1 b, while suppressing the etching of the insulatingfilm IL6 exposed. In particular, wet etching is more preferable.

Then, as shown in FIGS. 21 and 22, the sidewall spacers SW1 c, and theinsulating film IL6 are subjected to etching back (etching, dryetching), so that sidewall spacers (sidewalls, sidewall insulatingfilms) SW2 are formed as the sidewall insulating film over the sidewallsof the gate electrodes GE1, GE2, and GE3 (in step S15 shown in FIG. 2).

In the etching back process of step S15, the etching conditions arecontrolled to cause not only the anisotropic etching, but also the sideetching (isotropic etching). That is, in step S15, the sidewall spacerSW1 c and the insulating film IL6 are subjected to side etching as wellas the anisotropic etching. The balance between the anisotropic etchingand the side etching can be controlled by the kind of gas used for theetching, the flow rate of the gas, and the like.

Thus, in step S15, the sidewall spacer SW1 c and the insulating film IL6are subjected to the anisotropic etching, which decreases the thicknessof the insulating film. IL6 as viewed in the direction substantiallyperpendicular to the main surface of the semiconductor substrate SUB.Together with this, in step S15, the sidewall spacers SW1 c and theinsulating film IL6 are subjected to the side etching, which decreasesthe thicknesses of the sidewall spacers SW1 c and the insulating film.IL6 as viewed in the direction substantially parallel to the directionof the gate length of the gate electrodes (GE1, GE2, GE3).

In step S15, the sidewall spacers SW1 c are removed, so that theinsulating films IL6 are left over the sidewalls of the gate electrodesGE1, GE2, and GE3 to become the sidewall spacers SW2 with the insulatingfilm IL6 in other regions removed. Thus, the sidewall spacers SW2 areformed of the insulating film IL6 remaining over the sidewalls of thegate electrodes GE1, GE2, and GE3. In step S15, the insulating film IL6except for the parts of the insulating film IL6 remaining as thesidewall spacer SW2 over the sidewalls of the gate electrodes GE1, GE2,and GE3 can be removed.

In the above step S15, the entire sidewall spacers SW1 c are preferablyremoved not to leave the sidewall spacers SW1 c at all. As a result,after the end of the process in step S15, the sidewall spacers SW2 madeof the remaining insulating film IL6 are formed over the sidewalls ofthe gate electrodes GE1, GE2, and GE3 without the sidewall spacer SW1(which are not remaining). That is, after the end of the process in stepS15, the sidewall spacer SW2 formed on each sidewall of the gateelectrodes GE1, GE2, and GE3 is formed of not the insulating film IL6and the remaining part of the sidewall spacer SW1, but the single layerof the insulating film IL6.

In step S15, the etching back is preferably performed on the conditions(etching conditions) in which both the sidewall spacers SW1 c(insulating film IL7) and the insulating film IL6 are etched. When theinsulating film IL7 (sidewall spacer SW1 c) is the silicon oxide filmand the insulating film IL6 is the silicon nitride film, the etchingback process of step S15 can use the following etching gas by way ofexample. That is, for example, the etching gas for use can be a mixedgas of CF₄ gas, and Ar gas.

FIG. 21 shows the halfway stage of the etching process in step S15,specifically, the stage directly after removal of the entire sidewallspacer SW1 c during the etching process in step S15. FIG. 21 shows thestage directly after ending the etching process in step S15, followingthe stage shown in FIG. 20.

In the etching process of step S15, in the stage where the entiresidewall spacers SW1 c are removed, the insulating film IL6 preferablyremains in the form of layer over the semiconductor substrate SUB asshown in FIG. 21. After removing the entire sidewall spacers SW1 c inthe etching process of step S15, etching is preferably continued not toleave the insulating film IL6 in the form of layer over thesemiconductor substrate SUB. That is, the insulating film IL6 except forthe parts thereof serving as the sidewall spacer SW2 is removed.

When the offset spacers SP are formed over the sidewalls of the gateelectrodes GE1, GE2, and GE3, the sidewall spacer SW2 is formed overeach sidewall of the gate electrodes GE1, GE2, and GE3 via the offsetspacer SP.

The sidewall spacer SW2 formed over the sidewall of the gate electrodeGE1 among the sidewall spacers SW2 is hereinafter referred to as a“sidewall spacer SW2 a”. The sidewall spacer SW2 formed over thesidewall of the gate electrode GE2 among the sidewall spacers SW2 ishereinafter referred to as a “sidewall spacer SW2 b”. The sidewallspacer SW2 formed over the sidewall of the gate electrode GE3 among thesidewall spacers SW2 is hereinafter referred to as a “sidewall spacerSW2 c”.

A width T1 c of the sidewall spacer SW2 c is larger than a width T1 a ofthe sidewall spacer SW2 a, and larger than a width T1 b of the sidewallspacer SW2 b (that is, T1 c>T1 a, and T1 c>T1 b). In other words, thewidth T1 a of the sidewall spacer SW2 a is smaller than the width T1 cof the sidewall spacer SW2 c (T1 a<T1 c), and the width T1 b of thesidewall spacer SW2 b is smaller than the width T1 c of the sidewallspacer SW2 c (T1 b<T1 c). The width T1 a of the sidewall spacer SW2 a issubstantially equal to the width T1 b of the sidewall spacer SW2 b (thatis, T1 a=T1 b).

The width T1 a of the sidewall spacer SW2 a corresponds to a distance(distance measured in the direction parallel to the gate lengthdirection of the gate electrode GE1) between one side surface (sidesurface of the sidewall spacer SW2 a) opposed (adjacent) to the sidewallof the gate electrode GE1, and the other side surface (the other sidesurface of the sidewall spacer SW2) opposite to the above side surface,among the side surfaces of the sidewall spacer SW2 a. That is, the widthT1 a of the sidewall spacer SW2 a corresponds to the size (width) of thesidewall spacer SW2 a as measured at the lower part of the sidewall ofthe gate electrode GE1 in the direction parallel to the gate lengthdirection of the gate electrode GE1.

The width T1 b of the sidewall spacer SW2 b corresponds to a distance(distance measured in the direction parallel to the gate lengthdirection of the gate electrode GE2) between one side surface (sidesurface of the sidewall spacer SW2 b) opposed (adjacent) to the sidewallof the gate electrode GE2, and the other side surface (the other sidesurface of the sidewall spacer SW2 b) opposite to the above sidesurface, among the side surfaces of the sidewall spacer SW2 b. That is,the width T1 b of the sidewall spacer SW2 b corresponds to the size(width) of the sidewall spacer SW2 b as measured at the lower part ofthe sidewall of the gate electrode GE2 in the direction parallel to thegate length direction of the gate electrode GE2.

The width T1 c of the sidewall spacer SW2 c corresponds to a distance(distance measured in the direction parallel to the gate lengthdirection of the gate electrode GE3) between one side surface (sidesurface of the sidewall spacer SW2 c) opposed (adjacent) to the sidewallof the gate electrode GE3, and the other side surface (the other sidesurface of the sidewall spacer SW2 c) opposite to the above sidesurface, among the side surfaces of the sidewall spacer SW2 c. That is,the width T1 c of the sidewall spacer SW2 c corresponds to the size(width) of the sidewall spacer SW2 c as measured at the lower part ofthe sidewall of the gate electrode GE3 in the direction parallel to thegate length direction of the gate electrode GE3.

The width T1 a of the sidewall spacer SW2 a can be regarded as thethickness of the sidewall spacer SW2 a (thickness thereof over thesidewall of the gate electrode GE1). The width T1 b of the sidewallspacer SW2 b can be regarded as the thickness of the sidewall spacer SW2b (thickness thereof over the sidewall of the gate electrode GE2). Thewidth T1 c of the sidewall spacer SW2 c can be regarded as the thicknessof the sidewall spacer SW2 c (thickness thereof over the sidewall of thegate electrode GE2).

The following will be the reason why the width T1 a of the sidewallspacer SW2 a and the width T1 b of the sidewall spacer SW2 b are smallerthan the width T1 c of the sidewall spacer SW2 c (that is, T1 a<T1 c,and T1 b<T1 c).

In the etching process of step S15, not only the anisotropic etching,but also side etching is performed. Since in the high breakdown voltageMISFET formation region 1C, the sidewall spacer SW1 c is formed overeach side surface IL6 a of the insulating film IL6, the sidewall spacersSW1 c are mainly subjected to the side etching. Until the entiresidewall spacer SW1 c is removed, the side surface IL6 a of theinsulating film IL6 is not subjected to the side etching. That is, inthe high breakdown voltage MISFET formation region 1C, only after theremoval of the sidewall spacer SW1 c to expose the side surface IL6 a ofthe insulating film IL6 in the whole etching time of the step S15, theside surface IL6 a of the insulating film IL6 is subjected to the sideetching.

In contrast, in the low and intermediate breakdown voltage MISFETformation regions 1A and 1B, while the sidewall spacer SW1 is not formedover the side surface IL6 a of the insulating film IL6 (with thesidewall spacers SW1 a and SW1 b already removed), the etching in stepS15 is started. As a result, in the low and intermediate breakdownvoltage MISFET formation regions 1A and 1B, during the entire etchingtime of step S15, the side surface IL6 a of the insulating film IL6 isnot subjected to the side etching.

As compared to the high breakdown voltage MISFET formation region 1C,the side surface IL6 a of the insulating film IL6 in the low breakdownvoltage MISFET formation region 1A and the intermediate breakdownvoltage MISFET formation region 1B are subjected to the side etching fora long time. When the side surface IL6 a of the insulating film IL6 issubjected to the side etching, the longer the time of the side etching,the more the amount of the insulating film IL6 subjected to the sideetching (the thickness of the side etched film) becomes to make theinsulating film IL6 over each sidewall of the gate electrode thinner.

As a result, in the stage after the end of the etching in step S15, thethickness of the insulating film IL6 remaining over each sidewall of thegate electrodes GE1 and GE2 in the low and intermediate breakdownvoltage MIFSET formation regions 1A and 1B is smaller (thinner) thanthat of the insulating film IL6 remaining over the sidewall of the gateelectrode GE3 in the high breakdown voltage MISFET formation region 1C.That is, each of the widths T1 a and T1 b of the sidewall spacers SW2 aand SW2 b is smaller than the width T1 c of the sidewall spacer SW2 c(T1 c>T1 a, and T1 c>T1 b).

As mentioned above, in this embodiment, the etching process in step S15is performed with the sidewall spacer SW1 c remaining over each sidesurface IL6 a of the insulating film IL6 in the high breakdown voltageMISFET formation region 1C, and with the sidewall spacers SW1 a and SW1b removed from each side surface IL6 a of the insulating film IL6 in thelow and intermediate breakdown voltage MISFET formation regions 1A and1B. In the high breakdown voltage MISFET formation region 1C, thesidewall spacers SW1 c can serve as a prevention film of the sideetching of the insulating film IL6, and thus can decrease the amount ofside etching of the insulating film IL6 by reducing the side etchingtime of the insulating film IL6 as compared to in the low andintermediate breakdown voltage MISFET formation regions 1A and 1B. Sucha difference in amount of the side etching of the insulating film IL6between the MISFET formation regions decreases the thickness of theinsulating film IL6 over the sidewall of the gate electrode in the highbreakdown voltage MISFET formation region 1C as compared to in the lowand intermediate breakdown voltage MISFET formation regions 1A and 1B.As a result, the width T1 c of the sidewall spacer SW2 c can be madelarger than each of the widths T1 a and T1 b of the sidewall spacers SW2a and SW2 b.

In this way, the sidewall spacers SW2 (SW2 a, SW2 b, SW2 c) are formed.

The sidewall spacers SW2 are formed over the sidewalls of the gateelectrodes (gate electrodes GE1, GE2, and GE3) after forming theextension regions (extension regions EX1, EX2, and EX3) having a lowconcentration of impurities in the lightly doped drain (LDD) structure.The sidewall spacers SW2 are formed before ion implantation for formingsource and drain regions (specifically, source and drain regions SD1,SD2, and SD3 to be described later) having a high concentration ofimpurities in the LDD structure. In the ion implantation, the sidewallspacers SW2 serve as an ion implantation blocking mask.

Then, as shown in FIG. 23, the source and drain regions SD1, SD2, andSD3 which are n⁺-type semiconductor regions (n-type impurity diffusionlayer) are formed (in step S16 shown in FIG. 2).

The source and drain SD1 can be formed by ion-implanting p-typeimpurities, such as boron (B), in the semiconductor substrate SUB withinthe low breakdown voltage MISFET formation region 1A (this ionimplantation being hereinafter referred to as an “ion implantation IM3a”). FIG. 23 schematically shows the ion implantation IM3 a for formingthe source and drain regions SD1 by the arrow.

In the ion implantation IM3 a, the sidewall spacers SW2 a over thesidewalls of the gate electrode GE1 in the low breakdown voltage MISFETformation region 1A can serve as a mask (ion implantation blockingmask). The offset spacer SP is formed between the gate electrode GE1 andthe sidewall spacer SW2 a, and can also serve as the mask (ionimplantation blocking mask). Thus, the implantation of impurities areprevented in the ion implantation IM3 a into the regions directly underthe gate electrode GE1 and the sidewall spacers SW2 a over the sidewallsthereof (also directly under the offset spacer SP in the presence of theoffset spacer SP) in the semiconductor substrate SUB (n-type well NW1).

Thus, the source and drain regions SD1 are formed by ion-implantingp-type impurities, such as boron (B), into the regions on both sides ofthe gate electrode GE1 and sidewall spacers SW2 a over the sidewallsthereof in the semiconductor substrate SUB (n-type well NW1) within thelow breakdown voltage MISFET formation region 1A. Thus, the source anddrain regions SD1 in the low breakdown voltage MISFET formation region1A are aligned (self-aligned) with the side surfaces of the sidewallspacers SW2 a over the sidewalls of the gate electrode GE1. In the ionimplantation IM3 a, the p-type impurities can also be ion-implanted inthe gate electrode GE1 (silicon film forming the gate electrode).

The source and drain regions SD1 are the semiconductor region having thesame conduction type (herein of the p-type) as the extension region EX1,but have a higher concentration of impurities (p-type impurityconcentration) than that of the extension region EX1, and a deeper depth(junction depth) than that of the extension region EX1.

As a result, in the low breakdown voltage MISFET formation region 1A,the p-type semiconductor region (impurity diffusion layer) serving asthe source or drain of the p-channel MISFETQ1 is formed of thesource/drain region SD1 and extension region EX1. In other words, theextension region EX1 and the source or drain region SD1 having thehigher impurity concentration than the region EX1 serve as thesemiconductor region for the source or drain of the MISFETQ1 (p-typesemiconductor region). Thus, the source region and drain region of theMISFETQ1 form the LDD structure. As mentioned above, the extensionregion EX1 is formed to be self-aligned with the offset spacer SP overthe sidewall of the gate electrode GE. The source and drain regions SD1are formed to be self-aligned with the sidewall spacers SW2 a formedover the sidewalls of the gate electrode GE1 via the offset spacers SP.

The source and drain SD2 can be formed by ion-implanting p-typeimpurities, such as boron (B), in the semiconductor substrate SUB withinthe intermediate breakdown voltage MISFET formation region 1B (this ionimplantation being hereinafter referred to as “ion implantation IM3 b”).FIG. 23 schematically shows the ion implantation IM3 b for forming thesource and drain regions SD2 by the arrow.

In the ion implantation IM3 b, the gate electrode GE2 and the sidewallspacers SW2 a over the sidewalls of the gate electrode GE2 in theintermediate breakdown voltage MISFET formation region 1B can serve as amask (ion implantation blocking mask). When the offset spacer SP isformed between the gate electrode GE2 and the sidewall spacer SW2 b, theoffset spacer SP can also serve as the mask (ion implantation blockingmask). Thus, in the ion implantation IM3 b, the implantation ofimpurities are prevented in the regions directly under the gateelectrode GE2 and the sidewall spacers SW2 b over the sidewalls thereof(also directly under the offset spacer SP in the presence of the offsetspacer SP) in the semiconductor substrate SUB (n-type well NW2).

In the intermediate breakdown voltage MISFET formation region 1B, thesource and drain regions SD2 are formed by implanting p-type impurities,such as boron (B), into the regions on both sides of the gate electrodeGE2 and sidewall spacers SW2 b over the sidewalls thereof in thesemiconductor substrate SUB (n-type well NW2). Thus, the source anddrain regions SD2 are formed in the intermediate breakdown voltageMISFET formation region 1B to be aligned (self-aligned) with the sidesurfaces of the sidewall spacers SW2 b over the sidewalls of the gateelectrode GE2. In the ion implantation IM3 b, the p-type impurities canalso be ion-implanted in the gate electrode GE2 (silicon film formingthe gate electrode).

The source and drain regions SD2 are the semiconductor region having thesame conduction type (herein, the p-type) as the extension region EX2,but have a higher concentration of impurities (p-type impurityconcentration) than that of the extension region EX2, and a deeper depth(junction depth) than that of the extension region EX2.

Thus, in the intermediate breakdown voltage MISFET formation region 1B,the p-type semiconductor region (impurity diffusion layer) serving asthe source or drain of the p-channel MISFETQ2 is formed of thesource/drain region SD2 and extension region EX2. In other words, theextension region EX2 and the source or drain region SD2 having the highimpurity concentration serve as the semiconductor region for the sourceor drain of the MISFETQ2 (p-type semiconductor region). Thus, the sourceregion and drain region of the MISFETQ2 form the LDD (Lightly DopedDrain) structure. As mentioned above, the extension region EX2 is formedto be self-aligned with the gate electrode GE2. The source and drainregions SD2 are formed to be self-aligned with the sidewall spacers SW2b formed over the sidewalls of the gate electrode GE2.

The source and drain SD3 can be formed by ion-implanting p-typeimpurities, such as boron (B), in the semiconductor substrate SUB withinthe high breakdown voltage MISFET formation region 1C (this ionimplantation being hereinafter referred to as “ion implantation IM3 c”).FIG. 23 schematically shows the ion implantation IM3 c for forming thesource and drain regions SD3 by the arrow.

In the ion implantation IM3 c, the gate electrode GE3 and the sidewallspacers SW2 c over the sidewalls thereof in the high breakdown voltageMISFET formation region 1C can serve as a mask (ion implantationblocking mask). When the offset spacer SP is formed between the gateelectrode GE3 and the sidewall spacer SW2 c, the offset spacer SP canalso serve as the mask (ion implantation blocking mask). Theimplantation of impurities is prevented in the ion implantation IM3 c inthe regions directly under the gate electrode GE3 and the sidewallspacers SW2 c over the sidewalls thereof (also directly under the offsetspacer SP in the presence of the offset spacer SP) in the semiconductorsubstrate SUB (n-type well NW3).

Thus, the source and drain regions SD3 are formed in the high breakdownvoltage MISFET formation region 1C by ion-implanting p-type impurities,such as boron (B), into the regions on both sides of the gate electrodeGE3 and sidewall spacers SW2 c over the sidewalls thereof in thesemiconductor substrate SUB (n-type well NW3). Thus, the source anddrain regions SD3 in the high breakdown voltage MISFET formation region1C are formed to be aligned (self-aligned) with the side surfaces of thesidewall spacers SW2 c over the sidewalls of the gate electrode GE3. Thep-type impurities can also be ion-implanted in the gate electrode GE3(silicon film forming the gate electrode) in the ion implantation IM3 c.

The source and drain regions SD3 are the semiconductor region having thesame conduction type (herein, the p-type) as the extension region EX3,but have a higher concentration of impurities (p-type impurityconcentration) than that of the extension region EX3, and a deeper depth(junction depth) than that of the extension region EX3.

Thus, in the high breakdown voltage MISFET formation region 1C, thep-type semiconductor region (impurity diffusion layer) serving as thesource or drain of the p-channel MISFETQ3 is formed of the source/drainregion SD3 and extension region EX3. In other words, the extensionregion EX3 and the source and drain regions SD3 having the higherimpurity concentration than that of the region EX3 serve as thesemiconductor region for the source and drain of the MISFETQ3 (p-typesemiconductor region). Thus, the source region and drain region of theMISFETQ3 form the LDD (Lightly Doped Drain) structure. As mentionedabove, the extension region EX3 is formed to be self-aligned with thegate electrode GE3. The source and drain regions SD3 are formed to beself-aligned with the sidewall spacers SW2 c formed over the sidewallsof the gate electrode GE3.

The ion implantation IM3 a for forming the source and drain regions SD1,the ion implantation IM3 b for forming the source and drain regions SD2,and the ion implantation IM3 c for forming the source and drain regionsSD3 may be performed in the same ion implantation step, or can beperformed in different ion implantation steps. Two of the ionimplantations IM3 a, IM3 b, and IM3 c can be performed in the same ionimplantation step, but the remaining ion implantation can be performedin another ion implantation step.

When performing the ion implantations IM3 a, IM3 b, and IM3 c in thesame ion implantation step, the ion implantation is simultaneouslyperformed on the entire semiconductor substrate SUB in the low,intermediate, and high breakdown voltage MISFET formation regions 1A,1B, and 1C to thereby collectively form the source and drain regionsSD1, SD2, and SD3.

When the ion implantations IM3 a, IM3 b, and IM3 c are performed indifferent steps, each ion implantation is performed while forming aphotoresist layer so as to expose regions of interest for formation ofthe source and drain regions by the ion implantation among the low,intermediate, and high breakdown voltage MISFET formation regions 1A,1B, and 1C, and to cover the remaining regions with the photoresistlayer. For example, while the photoresist layer is formed to cover theintermediate and high breakdown voltage MISFET formation regions 1B and1C, and to expose the low breakdown voltage MISFET formation region 1A,the ion implantation IM3 a is performed on the semiconductor substrateSUB in the low breakdown voltage MISFET formation region 1A to therebyform the source and drain regions SD1. While the photoresist layer isformed to cover the low and high breakdown voltage MISFET formationregions 1A and 1C, and to expose the intermediate breakdown voltageMISFET formation region 1B, the ion implantation IM3 b is performed onthe semiconductor substrate SUB in the low breakdown voltage MISFETformation region 1B to thereby form the source and drain regions SD2.While the photoresist layer is formed to cover the low and intermediatebreakdown voltage MISFET formation regions 1A and 1B, and to expose thehigh breakdown voltage MISFET formation region 1C, the ion implantationIM3 c is performed on the semiconductor substrate SUB in the highbreakdown voltage MISFET formation region 1C to thereby form the sourceand drain regions SD3.

When the ion implantations IM3 b and IM3 c are performed in the samestep, and the ion implantation IM3 a is performed in another step amongthe ion implantations IM3 a, IM3 b, and IM3 c, for example, the ionimplantations may be performed in the following way. That is, while thephotoresist layer is formed to cover the intermediate and high breakdownvoltage MISFET formation regions 1B and 1C, and to expose the lowbreakdown voltage MISFET formation region 1A, the ion implantation IM3 ais performed on the semiconductor substrate SUB in the low breakdownvoltage MISFET formation region 1A to thereby form the source and drainregions SD1. While the photoresist layer is formed to cover the lowbreakdown voltage MISFET formation regions 1A, and to expose theintermediate and high breakdown voltage MISFET regions 1B and 1C,another ion implantation is performed on the semiconductor substrate SUBin the intermediate and high breakdown voltage MISFET formation regions1B and 1C to thereby collectively form the source and drain regions SD2and SD3.

Next, in order to active the impurities introduced by the ionimplantations, the annealing process (heat treatment) is performed (instep S17 shown in FIG. 2).

In this way, the MISFETQ1 is formed in the low breakdown voltage MISFETformation region 1A of the semiconductor substrate SUB, the MISFETQ2 isformed in the intermediate breakdown voltage MISFET formation region 1Bof the substrate, and the MISFETQ3 is formed in the high breakdownvoltage MISFET formation region 1C of the substrate.

In the low breakdown voltage MISFET formation region 1A, thesemiconductor regions for the source or drain of the MISFETQ1 are formedon both sides (both sides in the gate length direction) of the gateelectrode GE1 in the semiconductor substrate SUB. Each of thesemiconductor regions for the source or drain of the MISFETQ1 is formedof the extension region EX1 and the source/drain region SD1 having ahigher impurity concentration than that of the extension region. Thatis, in the semiconductor substrate SUB within the low breakdown voltageMISFET formation region 1A, (a pair of) the extension regions EX1 areformed in respective regions spaced apart from each other via a channelformation region. The source and drain regions SD1 each having a higherimpurity concentration than that of the extension region EX1 are formedoutside the respective extension regions EX1 (on the side apart from thechannel formation region). Thus, the extension region EX1 is adjacent tothe channel formation region, and the source/drain region SD1 is spacedapart from the channel formation region by the extension region EX1, andadjacent to the extension region EX1. The part of the semiconductorsubstrate SUB under the gate electrode GE1 becomes

a region where the channel of the MISFETQ1 (channel formation region) isformed. The gate electrode GE1 and the gate insulating film GI1 underthe gate electrode GE1 serve as the gate electrode and the gateinsulating film of the MISFETQ1, respectively.

In the intermediate breakdown voltage MISFET formation region 1B, thesemiconductor regions for the source and drain of the MISFETQ2 areformed on both sides (both sides in the gate length direction) of thegate electrode GE2 in the semiconductor substrate SUB. Each of thesemiconductor regions for the source or drain of the MISFETQ2 is formedof the extension region EX2 and the source/drain region SD2 having ahigher impurity concentration than that of the extension region. Thatis, in the semiconductor substrate SUB within the intermediate breakdownvoltage MISFET formation region 1B, (a pair of) the extension regionsEX2 are formed in respective regions spaced apart from each other via achannel formation region. The source and drain regions SD2 each having ahigher impurity concentration than that of the extension region EX2 areformed outside the respective extension regions EX2 (on the side apartfrom the channel formation region). Thus, the extension region EX2 isadjacent to the channel formation region, and the source/drain regionSD2 is spaced apart from the channel formation region by the extensionregion EX2, and adjacent to the extension region EX2. The part of thesemiconductor substrate SUB under the gate electrode GE2 becomes aregion where the channel of the MISFETQ2 (channel formation region) isformed. The gate electrode GE2 and the gate insulating film GI2 underthe gate electrode GE2 serve as the gate electrode and the gateinsulating film of the MISFETQ2, respectively.

In the high breakdown voltage MISFET formation region 1C, thesemiconductor regions for the source and drain of the MISFETQ3 areformed on both sides (both sides in the gate length direction) of thegate electrode GE3 in the semiconductor substrate SUB. Each of thesemiconductor regions for the source or drain of the MISFETQ3 is formedof the extension region EX3 and the source/drain region SD3 having ahigher impurity concentration than that of the extension region. Thatis, in the semiconductor substrate SUB within the high breakdown voltageMISFET formation region 1C, (a pair of) the extension regions EX3 areformed in respective regions spaced apart from each other via a channelformation region. The source and drain regions SD3 each having a higherimpurity concentration than that of the extension region EX3 are formedoutside the respective extension regions EX3 (on the side apart from thechannel formation region). Thus, the extension region EX3 is adjacent tothe channel formation region, and the source/drain region SD3 is spacedapart from the channel formation region by the extension region EX3, andadjacent to the extension region EX3. The part of the semiconductorsubstrate SUB under the gate electrode GE3 becomes a region where thechannel of the MISFETQ3 (channel formation region) is formed. The gateelectrode GE3 and the gate insulating film GI3 under the gate electrodeGE3 serve as the gate electrode and the gate insulating film of theMISFETQ3, respectively.

As mentioned above, the widths T1 a and T1 b of the sidewall spacers SW2a and SW2 b are smaller than the width T1 c of the sidewall spacer SW2 c(T1 a<T1 c, and T1 b<T1 c). Reflecting the above arrangement, thedistance (gap) between the source/drain region SD1 and the channelformation region (channel formation region directly under the gateelectrode GE1) in the low breakdown voltage MISFET formation region 1Ais smaller than that between the source/drain region SD3 and the channelformation region (channel formation region directly under the gateelectrode GE3) in the high breakdown voltage MISFET formation region 1C.Thus, the width (size) of the extension region EX1 measured in the gatelength direction of the gate electrode GE1 is smaller than that of theextension region EX3 measured in the gate length direction of the gateelectrode GE3. The distance (gap) between the source/drain region SD2and the channel formation region (channel formation region directlyunder the gate electrode GE2) in the intermediate breakdown voltageMISFET formation region 1B is smaller than that between the source/drainregion SD3 and the channel formation region (channel formation regiondirectly under the gate electrode GE3) in the high breakdown voltageMISFET formation region 1C. Thus, the width (size) of the extensionregion EX2 measured in the gate length direction of the gate electrodeGE2 is smaller than that of the extension region EX3 measured in thegate length direction of the gate electrode GE3.

Then, as shown in FIG. 24, a metal salicide layer MS having a lowresistance is formed over the front surface (superficial layer, upperlayer) of each of the gate electrodes GE1, GE2, and GE3 and the sourceand drain regions SD1, SD2, and SD3 by a self-aligned silicide(Salicide) technique (in step S18 shown in FIG. 2).

After exposing the front surface (upper surface) of each of the gateelectrodes GE1, GE2, and GE3 and the source and drain regions SD1, SD2,and SD3, for example, a metal film, such as a cobalt film, a nickelfilm, or a nickel platinum alloy film, is formed over the semiconductorsubstrate SUB to cover the gate electrode GE1, GE2, and GE3 and thesidewall spacers SW2 a, SW2 b, and SW2 c.

Then, the heat treatment is performed on the substrate to react themetal film with the upper layers of the gate electrode GE1, GE2, and GE3and the source and drain regions SD1, SD2, and SD3. As a result, themetal silicide layer MS can be formed over the front surface (frontlayer part, upper layer) of each of the gate electrodes GE1, GE2, andGE3 and the source and drain regions SD1, SD2, and SD3. Thereafter, thenon-reacted metal film is removed, which is illustrated in FIG. 24. Theformation of the metal silicide layer MS can decrease the resistance,including diffusion resistance or contact resistance of the source anddrain regions SD1, SD2, and SD3.

Then, as shown in FIG. 25, an insulating film (interlayer insulatingfilm) IL8 is formed over the main surface of the semiconductor substrateSUB. That is, the insulating film IL8 is formed over the semiconductorsubstrate SUB including the metal silicide layer MS to cover the gateelectrodes GE1, GE2, and GE3 and the sidewall spacers SW2 a, SW2 b, andSW2 c. The insulating film IL8 is formed of, for example, a singlesilicon oxide film, or a lamination of a silicon nitride film and asilicon oxide film thicker than the silicon nitride film (the siliconnitride film being located as a lower layer, and the silicon oxide filmbeing located as an upper layer). Then, by polishing the front surface(upper surface) of the insulating film IL8 by the CMP method, the uppersurface of the insulating film. IL8 is planarized. Even when theconcavities and convexities are formed on the surface of the insulatingfilm IL8 due to the presence of bumps of the underlayer, the interlayerinsulating film having a flat surface can be obtained by polishing thefront surface of the insulating film IL8 by the CMP method.

Then, as shown in FIG. 26, the insulating film IL8 is dry etched using aphotoresist layer (not shown) formed over the insulating film IL8 as anetching mask to thereby form contact holes (through holes, openings) CTin the insulating film IL8. Parts of the main surface of thesemiconductor substrate SUB, for example, parts of the metal silicidelayer MS over the front surface of each of the source and drain regionsSD1, SD2, and SD3, and parts of the metal silicide layer MS on the frontsurface of the gate electrodes GE1, GE2, and GE3, are exposed at thebottoms of the contact holes CT.

Then, a conductive plug (conductor for connection) PG is formed oftungsten (W) in each contact hole CT. In order to form the plug PG, forexample, a barrier conductive film (for example, a titanium film, atitanium nitride film, or a lamination thereof) is formed over theinsulating film IL8 including the inside (bottom and sidewalls) of eachcontact hole CT by sputtering or plasma CVD method. Then, the mainconductive film is formed of a tungsten film over the barrier conductivefilm by the CVD method to fill in the contact hole CT. Then, unnecessaryparts of the main conductive film and barrier conductive film locatedoutside the contact hole CT (over the insulating film IL8) are removedby the CMP method or etching back. As a result, the upper surface of theinsulating film IL8 is exposed, and the plug PG is formed of the barrierconductive film and the main conductive film filling and remaining inthe contact hole CT of the insulating film IL8. For simplifying thefigure, as shown in FIG. 26, the plug PG is illustrated to be comprisedof integration of the main conductive film and the barrier conductivefilm. The plug PG is electrically coupled to the metal silicide layer MSat its bottom over the front surface of each of the gate electrode GE1,GE2, and GE3, and the source and drain regions SD1, SD2, and SD3.

Then, as shown in FIG. 27, an insulating film IL9 for formation ofwirings is formed over the insulating film IL8 with the plugs PGembedded therein. The insulating film IL9 can be a single film (singleinsulating film) or a laminated film (laminated insulating film).

Then, a wiring M1 is formed as a first wiring layer by a singledamascene method. Specifically, the wiring M1 can be formed in thefollowing way. First, a wiring trench is formed in a predeterminedregion of the insulating film IL9 by dry etching using a photoresistlayer (not shown) as a mask. Then, a barrier conductive film (forexample, a titanium nitride film, a tantalum film, or a tantalum nitridefilm) is formed over the insulating film IL9 including the bottom andsidewalls of the wiring trench. Subsequently, a copper seed layer isformed over the barrier conductive film by the CVD or sputtering, andthen a copper plating film is formed over the seed layer by electrolyticplating or the like, so that the copper plating film fills the trench.Thereafter, the main conductive film (copper plating film and seedlayer) and barrier conductive film except for those located in thewiring trenches are removed by the CMP method to thereby form the firstwiring layer M1 filled in the wiring trench and containing copper as amain conductive material. For simplifying the figure, FIG. 27 showsintegration of the copper plating film, the seed layer, and the barriermetal film as the wiring M1.

The wiring M1 is coupled to the plug PG, and electrically coupled to thesource/drain region SD1, SD2, or SD3, or the gate electrode GE1, GE2, orGE3 via the plug PG.

Thereafter, a second wiring layer is formed by the dual damascenemethod. However, the illustration and description thereof will beomitted below. Wirings following the first wiring layer M1 and thesecond wiring layer are not limited to a damascene wiring. The wiringcan also be formed by patterning a conductive film for wiring, and canbe, for example, a tungsten wiring or aluminum wiring.

In the way described above, the semiconductor device of this embodimentis manufactured.

<Manufacturing Procedure of Semiconductor Device in Examined Examples>

Next, examples examined by the inventors will be described.

FIGS. 28 to 31 are cross-sectional views of main parts of manufacturingsteps of the semiconductor device in a first examined example. In thefirst examined example, the semiconductor substrate SUB 101corresponding to the semiconductor substrate SUB of this embodimentincludes a low breakdown voltage MISFET formation region 101A in whichthe MISFET having a low breakdown voltage is formed, and a highbreakdown voltage MISFET formation region 101C in which the MISFEThaving a high breakdown voltage is formed.

In the first examined example, as shown in FIG. 28, element isolationregions ST101 corresponding to the element isolation regions ST areformed over the semiconductor substrate SUB101. An n-type well NW101 isformed in the semiconductor substrate SUB101 within the low breakdownvoltage MISFET formation region 101A. An n-type well NW103 is formed inthe semiconductor substrate SUB101 within the high breakdown voltageMISFET formation region 101C. A gate electrode GE101 is formed over thesemiconductor substrate SUB101 (n-type well NW101) within the lowbreakdown voltage MISFET formation region 101A via the gate insulatingfilm GI101. A gate electrode GE103 is formed over the semiconductorsubstrate SUB101 (n-type well NW103) within the high breakdown voltageMISFET formation region 101C via the gate insulating film GI103. Thethickness of the gate insulating film GI103 is larger than that of thegate insulating film GI101. A p-type extension region EX101 is formed inthe semiconductor substrate SUB101 within the low breakdown voltageMISFET formation region 101A by ion implantation. A p⁻-type extensionregion EX103 is formed in the semiconductor substrate SUB101 within thehigh breakdown voltage MISFET formation region 101C by ion implantation.

After obtaining the structure shown in FIG. 28 in this way, sidewallspacers SW102 a and SW102 c are formed over the sidewalls of the gateelectrodes GE101 and GE103, respectively. The sidewall spacers SW102 aand SW102 c are formed in the following way.

First, as shown in FIG. 29, an insulating film IL106 is formed over thesemiconductor substrate SUB101 to cover the gate electrodes GE101 andGE103. Then, as shown in FIG. 30, the insulating film IL106 is etchedback by anisotropic etching to leave the insulating film IL106 over eachsidewall of the gate electrodes GE101 and GE103 and to remove theinsulating film. IL106 in the remaining regions. Thus, the sidewallspacers SW102 a and SW102 c are formed which include the insulating filmIL106 remaining over the sidewalls of the gate electrodes GE101 andGE103. The sidewall spacer SW102 a is formed over each sidewall of thegate electrode GE101. The sidewall spacer SW102 c is formed over eachsidewall of the gate electrode GE103.

After forming the sidewall spacers SW102 a and SW102 c in this way, asshown in FIG. 31, the source and drain regions SD101 and SD103 areformed by the ion implantation. The source/drain regions SD101 is asemiconductor region having the same conduction type (herein, thep-type) as the extension region EX101, and having a higher concentrationof impurities than that of the extension region EX103.

The source/drain region SD103 is a semiconductor region having the sameconduction type (herein of the p-type) as the extension region EX103,and having a higher concentration of impurities than that of theextension region EX101.

In the ion implantation for forming the source and drain regions SD101,the gate electrode GE101 and the sidewall spacers SW102 a over thesidewalls thereof in the low breakdown voltage MISFET formation region101A can serve as the mask (ion implantation blocking mask). Thus, inthe low breakdown voltage MISFET formation region 101A, the source/drainregion SD101 is formed to be aligned (self-aligned) to the side surfaceof the sidewall spacer SW102 a over the sidewall of the gate electrodeGE101. In the ion implantation for forming the source and drain regionsSD103, the gate electrode GE103 and the sidewall spacers SW102 c overthe sidewalls thereof in the high breakdown voltage MISFET formationregion 101C can serve as the mask (ion implantation blocking mask).Thus, the source/drain regions SD103 in the high breakdown voltageMISFET formation region 101C are formed to be aligned (self-aligned)with the side surfaces of the sidewall spacers SW102 c over thesidewalls of the gate electrode GE103.

Thereafter, the salicide process form those corresponding to the metalsilicide layer MS, the insulating film IL8, the contact hole CT, and theplug PG. The illustration and description thereof will be omitted below.

In the first examined example shown in FIGS. 28 to 31, the width T101 aof the sidewall spacer SW102 a formed over the sidewall of the gateelectrode GE101 in the low breakdown voltage MISFET formation region101A is the same as the width T101 c of the sidewall spacer SW102 cformed over the sidewall of the gate electrode GE103 in the highbreakdown voltage MISFET formation region 101C (that is, T101 a=T101 c).

In the first examined example, the insulating film IL106 is formed tohave the same thickness between in the low breakdown voltage MISFETformation region 101A and the high breakdown voltage MISFET formationregion 101C. The insulating film IL106 is etched back to have the sameetched state between in the low breakdown voltage MISFET formationregion 101A and the high breakdown voltage MISFET formation region 101C.The width T101 c of the sidewall spacer SW102 c is the same as the widthT101 a of the sidewall spacer SW102 a (that is, T101 c=T101 a).

In order to improve the performance of the semiconductor device as muchas possible, however, the width of the sidewall spacer formed on eachsidewall of the gate electrodes is required to differ according to thetype of the MISFET.

For example, the low breakdown voltage MISFET is required to enhance thecurrent driving force, whereas the high breakdown voltage MISFET isrequired to enhance the breakdown voltage. Desirably, a certain distancebetween the source/drain region SD103 and the channel formation regionin the high breakdown voltage MISFET is ensured, while

a distance between the source/drain region SD101 and the channelformation region in the low breakdown voltage MISFET is not excessivelylarge. Thus, the distance between the source/drain region SD103 and thechannel formation region in the high breakdown voltage MISFET can bepreferably larger than that between the source/drain region SD101 andthe channel formation region in the low breakdown voltage MISFET tothereby improve the total performance of the semiconductor device.

However, when the width T101 c of the sidewall spacer SW102 c is set thesame as the width T101 a of the sidewall spacers SW102 a (T101 c=T101a), the distance between the channel formation region and thesource/drain region (SD101, SD103) in the low breakdown voltage MISFETbecomes the same as that in the high breakdown voltage MISFET.

For this reason, a technique is studied for differing the width of thesidewall spacer formed over the sidewall of the gate electrode betweenthe low breakdown voltage MISFET formation region 101A and the highbreakdown voltage MISFET formation region 101 c. FIGS. 32 to 37 arecross-sectional views of main parts of manufacturing steps of thesemiconductor device in a second studied example.

The second examined example can obtain the structure shown in FIG. 28 inthe same way as the first example. In the second examined example, asshown in FIGS. 32 to 36, the sidewall spacers SW202 a and SW202 c areformed over the sidewalls of the gate electrodes GE101 and GE103. Theformation of sidewall spacers SW202 a and SW202 c will be specificallydescribed below.

First, as shown in FIG. 32, an insulating film IL206 is formed over thesemiconductor substrate SUB101 to cover the gate electrodes GE101 andGE103. Then, as shown in FIG. 33, a photoresist layer PR201 is formedover the insulating film IL206 to cover the high breakdown voltageMISFET formation region 101C and to expose the low breakdown voltageMISFET formation region 101A.

Then, as shown in FIG. 34, the insulating film IL206 is etched using thephotoresist layer PR201 as a mask (etching mask). At this time, theetching is not performed through the entire thickness of the insulatingfilm IL206, but continued halfway through the entire thickness of theinsulating film IL206. As a result, the insulating film IL206 in thehigh breakdown voltage MISFET formation region 101C is not etched, butthe insulating film IL206 in the low breakdown voltage MISFET formationregion 101A is continuously etched up to the halfway through the entirethickness of the insulating film. Thus, a thickness T201 a of theinsulating film IL206 in the low breakdown voltage MISFET formationregion 101A is thinner than a thickness T201 c of the insulating filmIL206 in the high breakdown voltage MISFET formation region 101C. Thatis, T201 a<T201 c. The thicknesses T201 a and T201 c are shown in FIG.35.

Thereafter, as shown in FIG. 35, the photoresist layer PR201 is removed.As shown in FIG. 36, the insulating film IL206 is etched back to leavethe insulating film IL206 over each sidewall of the gate electrodesGE101 and GE103 and to remove the insulating film IL206 located in theremaining regions. Thus, the sidewall spacers SW202 a and 202 c areformed of the insulating film IL206 remaining over the sidewalls of thegate electrodes GE101 and GE103. The sidewall spacers SW202 a are formedover the sidewalls of the gate electrode GE101, and the sidewall spacersSW202 c are formed over the sidewalls of the gate electrode GE103.

After forming the sidewall spacers SW202 a and SW202 c in this way,manufacturing steps in the second examined example are the same as thosein the first examined example. That is, like the first examined example,the second examined example also form the source and drain regions SD101and SD103 by the ion implantation as shown in FIG. 37.

In the second examined example shown in FIGS. 32 to 37, the insulatingfilm IL206 in the low breakdown voltage MISFET formation region 101A isformed to have substantially the same thickness as that in the highbreakdown voltage MISFET formation region 101C (see FIG. 32). Then, thethickness T201 a of the insulating film IL206 in the low breakdownvoltage MISFET formation region 101A is thinner than the thickness T201c of the insulating film IL106 in the high breakdown voltage MISFETformation region 101C (see FIG. 34). Thereafter, the insulating filmIL206 is etched back to thereby form the sidewall spacers SW202 a andSW202 c. The difference between the thicknesses T201 a and T201 c of theinsulating film IL206 reflects the widths T202 a and T202 c of thesidewall spacers SW202 a and SW202 c, respectively. As a result, thewidth T202 a of the sidewall spacer SW202 a in the low breakdown voltageMISFET formation region 101A can be made smaller than the width T202 cof the sidewall spacer SW202 c in the high breakdown voltage MISFETformation region 101C (T202 a<T202 c).

In the second examined example, however, as shown in FIG. 35, thethickness T201 a of the insulating film IL206 in the low breakdownvoltage MISFET formation region 101A is made thinner than the thicknessT201 c of the insulating film IL106 in the high breakdown voltage MISFETformation region 101C, and then the insulating film IL206 is etched backto thereby form sidewall spacers SW202 a and SW202 c as shown in FIG.36. Thus, in the etching back process of the insulating film IL206 shownin FIG. 36, the etching is continued also in the low breakdown voltageMISFET formation region 101A until the insulating film IL206 located ina region other than the sidewalls of the gate electrode GE103 in thehigh breakdown voltage MISFET formation region 101C is removed. As aresult, the thickness 201 a of the insulating film IL206 in the lowbreakdown voltage MISFET formation region 101A is thinner than thethickness T201 c of the insulating film IL106 in the high breakdownvoltage MISFET formation region 101C. Thus, even after the insulatingfilm IL206 in the region other than the sidewalls of the gate electrodeGE101 in the low breakdown voltage MISFET formation region 101A iscompletely removed, the etching process might be continued. This leadsto overetching of the semiconductor substrate SUB101 in the lowbreakdown voltage MISFET formation region 101A, causing the damage onthe semiconductor substrate SUB101, which might reduce the performanceor reliability of the MISFET formed in the low breakdown voltage MISFETformation region 101A. This might also lead to the reduction inreliability of the manufactured semiconductor device.

Main Features and Effects of Present Embodiments

In this embodiment, in step S11, the insulating film IL6 is formed overthe semiconductor substrate SUB to cover the gate electrodes GE1, GE2,and GE3, and then in step S12, the insulating film IL7 is formed ofdifferent material from that of the insulating film IL6, over theinsulating film IL6. Then, in step S13, the insulating film IL7 isetched back to thereby form the sidewall spacers SW1 a, SW1 b, and SW1 cserving as the sidewall insulating film. The sidewall spacers SW1 a, SW1b, and SW1 c each are formed of the insulating film IL7 remaining on therespective side surfaces IL6 a of the insulating films IL6. Among thesidewall spacers, the sidewall spacer SW1 a is formed over the sidesurface IL6 a of the insulating film IL6 corresponding to each sidewallof the gate electrode GE1. The sidewall spacer SW1 b is formed over theside surface IL6 a of the insulating film IL6 corresponding to eachsidewall of the gate electrode GE2. The sidewall spacer SW1 c is formedover the side surface IL6 a of the insulating film IL6 corresponding toeach sidewall of the gate electrode GE3. In step S14, the sidewallspacers SW1 a and SW1 b are removed to leave the sidewall spacers SW1 c.Thereafter, in step S15, the sidewall spacers SW1 c and the insulatingfilm IL6 are etched back to thereby form the sidewall spacers SW2 a, SW2b, and SW2 c over the respective sidewalls of the gate electrodes GE1,GE2, and GE3. Among the sidewall spacers, the sidewall spacer SW2 a isformed of the insulating film IL6 remaining over each sidewall of thegate electrode GE1. The sidewall spacer SW2 b is formed of theinsulating film IL6 remaining over each sidewall of the gate electrodeGE2. The sidewall spacer SW2 c is formed of the insulating film IL6remaining over each sidewall of the gate electrode GE3. The relationshipamong the widths T1 a, T1 b, and T1 c of the thus-formed sidewallspacers SW2 a, SW2 b, and SW2 c is that each of the width T1 a of thesidewall spacer SW2 a and the width T1 b of the sidewall spacer SW2 b issmaller than the width T1 c of the sidewall spacer SW2 c (that is, T1a<T1 c, T1 b<T1 c).

The above and following brief description will be given about the reasonwhy each of the width T1 a of the sidewall spacer SW2 a and the width T1b of the sidewall spacer SW2 b is smaller than the width T1 c of thesidewall spacer SW2 c (that is, T1 a<T1 c, T1 b <T1 c).

That is, in steps S12 and S13, the sidewall spacers SW1 a, SW1 b, andSW1 c are formed. In step S14, the sidewall spacers SW1 a and SW1 b areremoved to leave the sidewall spacer SW1 c. Then, in step S15, thesidewall spacer SW1 c and the insulating film IL6 are etched back. Sincein the etching back process of step S15, the insulating film IL6 overthe sidewalls of the gate electrode GE3 is not subjected to the sideetching until the sidewall spacer SW1 c is removed, the amount of sideetching of the insulating film IL6 over the sidewalls of the gateelectrodes GE1 and GE2 is larger than that over the sidewalls of thegate electrode GE3. Such a difference in amount of the side etching ofthe insulating film IL6 between the gate electrodes reflect thefollowing features: each of the width T1 a of the sidewall spacer SW2 aand the width T1 b of the sidewall spacer SW2 b is smaller than thewidth T1 c of the sidewall spacer SW2 c (that is, T1 a<T1 c, T1 b<T1 c).

In this way, this embodiment can make the width T1 a of the sidewallspacer SW2 a and the width T1 b of the sidewall spacer SW2 b smallerthan the width T1 c of the sidewall spacer SW2 c (T1 a<T1 c, and T1 b<T1c).

Reflecting the difference between the width T1 a of the sidewall spacerSW2 a and the width T1 c of the sidewall spacer SW2 c, a distance(specifically, the distance in the direction parallel to the gate lengthdirection) between the source/drain region SD1 and the channel formationregion in the MISFETQ1 can be smaller than that (that is, the distancein the direction parallel to the gate length direction) between thesource/drain region SD3 and the channel formation region in theMISFETQ3. Reflecting the difference between the width T1 b of thesidewall spacer SW2 b and the width T1 c of the sidewall spacer SW2 c, adistance (specifically, the distance in the direction parallel to thegate length direction) between the source/drain region SD2 and thechannel formation region in the MISFETQ2 can be smaller than that(specifically, the distance in the direction parallel to the gate lengthdirection) between the source/drain region SD3 and the channel formationregion in the MISFETQ3.

Thus, the size (specifically, the size in the gate length direction) ofthe extension region EX1 having a low impurity concentration andextending between the source/drain region SD1 and the channel formationregion in the MISFETQ1 can be smaller than that (specifically, thedistance in the direction parallel to the gate length direction) of theextension region EX3 having a low impurity concentration and extendingbetween the source/drain region SD3 and the channel formation region inthe MISFETQ3. Thus, the size (specifically, the size in the gate lengthdirection) of the extension region EX2 having a low impurityconcentration and extending between the source/drain region SD2 and thechannel formation region in the MISFETQ2 can be smaller than that(specifically, the distance in the direction parallel to the gate lengthdirection) of the extension region EX3 having a low impurityconcentration and extending between the source/drain region SD3 and thechannel formation region in the MISFETQ3.

Desirably, the MISFETQ3 can ensure a certain distance between thesource/drain region SD3 and the channel formation region, and canimprove its breakdown voltage. In contrast, the MISFETQ1 and Q2 candecrease the distance between the source/drain region (SD1, SD2) and thechannel formation region as compared to that in the MISFETQ3 to therebyimprove the current driving force of the MISFETQ1 and Q2. Thus, thetotal performance of the semiconductor device can be improved.

In this embodiment, in step S12, the insulating film IL7 is formed, andthen in step S13, the insulating film IL7 is etched back to thereby formthe sidewall spacers SW1 a, SW1 b, and SW1 c. In step S13, in the lowbreakdown voltage MISFET formation region 1A, the intermediate breakdownvoltage MISFET formation region 1B, and the high breakdown voltageMISFET formation region 1C, the respective insulating films IL7 exceptfor the sidewall spacers SW1 a, SW1 b, SW1 c are removed to expose theinsulating films IL6 substantially at the same timing. Thus, the amountsof the overetching of the respective insulating films IL6 aresubstantially the same. In the stage where the sidewall spacers SW1 a,SW1 b, and SW1 c are formed in step S13, the thicknesses of therespective insulating films IL6 in the low, intermediate, and highbreakdown voltage MISFET formation regions 1A, 1B, and 1C can besubstantially the same. Thus, in etching back the sidewall spacer SW1 cand the insulating film IL6 in step S15, the insulating films IL6located except for the sidewalls of the gate electrodes (GE1, GE2, GE3)can be removed at the same timing in the low, intermediate, and highbreakdown voltage MISFET formation regions 1A, 1B, and 1C. Thisarrangement can suppress or prevent the excessive overetching in any oneof the low, intermediate, and high breakdown voltage MISFET formationregions 1A, 1B, and 1C to thereby suppress or prevent the damage on thesemiconductor substrate SUB in the etching back step of step S15. Thisembodiment can suppress or prevent the overetching of the semiconductorsubstrate SUB in the low, intermediate, and high breakdown voltageMISFET formation regions 1A, 1B, and 1C to thereby suppress or preventthe damage on the substrate SUB, and thus can improve the reliability ofthe manufactured semiconductor device.

In this embodiment, in step S14, the sidewall spacers SW1 a and SW1 bare removed to leave the sidewall spacer SW1 c. Then, in step S15, thesidewall spacer SW1 c and the insulating film IL6 are etched back. Inperforming etching to remove the sidewall spacers SW1 a and SW1 b, whileleaving the sidewall spacer SW1 c in step S14, the sidewall spacers SW1a and SW1 b are desirably etched and removed, while suppressing theetching of the insulating film IL6 as much as possible. This arrangementcan appropriately suppress or prevent the difference in thickness of theinsulating film IL6 among the low, intermediate, and high breakdownvoltage MISFET formation regions 1A, 1B, and 1C in the stage of removingthe sidewall spacers SW1 a and SW1 b in step S14. Thus, upon etchingback the sidewall spacer SW1 c and the insulating film IL6 in step S15,in the low, intermediate, and high breakdown voltage MISFET formationregions 1A, 1B, and 1C, the respective insulating films IL6 except forthose located over the sidewalls of the gate electrodes (GE1, GE2, GE3)can be removed at the same timing with more accuracy. This embodimentcan accurately suppress or prevent the damage on the semiconductorsubstrate SUB due to the excessive overetching in any one of the low,intermediate, and high breakdown voltage MISFET formation regions 1A,1B, and 1C in the etching back process of step S15.

As mentioned above, in performing etching to remove the sidewall spacersSW1 a and SW1 b and maintain the sidewall spacer SW1 c in step S14, theetching of the insulating film IL6 is desirably suppressed as much aspossible. From this point, the process in step S14 preferably selectsetching conditions that set an etching selectivity of the sidewallspacers SW1 a and SW1 b (insulating film IL7) with respect to theinsulating film IL6 to more than 1. The etching selectivity of 1.5 ormore is more preferable.

In performing etching to remove the sidewall spacers SW1 a and SW1 b andto remain the sidewall spacers SW1 c in step S14, wet etching ispreferably used to surely remove the sidewall spacers SW1 a and SW1 b,while suppressing the etching of the insulating film IL6 as much aspossible.

The etching back process in step S13 preferably uses the dry etching,which facilitates the formation of the sidewall spacers SW1 a, SW1 b,and SW1 c. The etching back process in step S15 preferably uses the dryetching, which facilitates the formation of the sidewall spacers SW2 a,SW2 b, and SW2 c.

Preferably, one of the insulating film IL6 and the insulating film IL7is a silicon oxide film, and the other is a silicon nitride film, whichcan easily improve the etching selectivity of the insulating film IL7(sidewall spacer SW1) with respect to the insulating film IL6. Thus, theprocess in step S14 easily removes the entire sidewall spacers SW1 a andSW1 b, while suppressing the etching of the insulating film IL6 as muchas possible. Further, the etching of the insulating film IL6 can besuppressed or prevented in the process of step S13.

Although preferably, one of the insulating film IL6 and the insulatingfilm IL7 is a silicon oxide film and the other is a silicon nitridefilm, in another embodiment, one of the insulating films IL6 and IL7 canbe a silicon oxide film or a silicon nitride film, and the other can bea silicon oxynitride film. In a further embodiment, the insulating filmsIL6 and IL7 can be formed of silicon oxynitride films with differentcompositions.

When the etching rate of the sidewall spacer SW1 c (insulating film IL7)is too slow in the etching back process of step S15, the insulating filmIL6 over the semiconductor substrate SUB except for those located overthe sidewalls of the gate electrodes GE1, GE2, and GE3 might be removedbefore removing the entire sidewall spacer SW1 c. In this case, theetching might be continued (until the entire sidewall spacer SW1 c isremoved and the sidewall spacers SW2 a, SW2 b, and SW2 c are formed)with the insulating film IL6 over the semiconductor substrate SUBremoved except for over the sidewalls of the gate electrodes GE1, GE2,and GE3. This might lead to the damage of the semiconductor substrateSUB due to the overetching of the substrate.

For this reason, as shown in FIG. 21, in step S15, the etching rate ofthe sidewall spacer SW1 c (insulating film IL7) is preferably increasedto such a certain level that leaves the insulating film IL6 over thesemiconductor substrate SUB in the form of layer upon completelyremoving the entire sidewall spacer SW1 c. In other words, in step S15,the respective etching rates of the sidewall spacer SW1 c and theinsulating film IL6 are preferably adjusted so as to leave theinsulating film IL6 over the semiconductor substrate SUB in the form oflayer upon completely removing the entire sidewall spacer SW1 c. Thiscan leave the insulating film IL6 over the semiconductor substrate SUBin the form of layer upon completely removing the entire sidewall spacerSW1 c in step S15 to thereby prevent the exposure of the semiconductorsubstrate SUB. The process in step S15 can suppress or prevent theoveretching of the semiconductor substrate SUB.

That is, in step S15, upon completely removing the entire sidewallspacer SW1 c, the insulating film IL6 is left over the semiconductorsubstrate SUB in the form of layer. Then, the etching process iscontinued. Thereafter, the etching is preferably stopped when thelayered insulating film IL6 is preferably etched and removed (that is,in the stage where the insulating film IL6 located over thesemiconductor substrate SUB except over the sidewalls of the gateelectrodes GE1, GE2, and GE3 is removed). This arrangement can form thesidewall spacers SW2 a, SW2 b, and SW2 c, while accurately suppressingor preventing the overetching of the semiconductor substrate SUB.

The excessive etching rate of the sidewall spacer SW1 c (insulating filmIL7) is too fast in step S15, which leads to a small difference betweenthe thickness of the insulating film IL6 over the sidewalls of the gateelectrodes GE1 and GE2, and the thickness of the insulating film IL6over the sidewall of the gate electrode GE3 upon completely removing theentire sidewall spacers SW1 c. In this case, a difference between thewidth T1 c of the sidewall spacer SW2 c and each of the widths T1 a andT1 b of the sidewall spacers SW2 a and SW2 b becomes smaller.

In the stage where the entire sidewall spacers SW1 c are removed in stepS15 as shown in FIG. 21, each of the thickness T2 a of the insulatingfilm IL6 over the sidewall of the gate electrode GE1, and

the thickness T2 b of the insulating film IL6 over the sidewall of thegate electrode GE2 is preferably thinner than the thickness T2 c of theinsulating film IL6 over the sidewall of the gate electrode GE3 by 3 nmor more. That is, in the stage where the entire sidewall spacers SW1 care removed, the following relationships are preferably satisfied: T2a≦T2 c−3 nm, and T2 b≦T2 c−3 nm. In other words, in the stage where theentire sidewall spacers SW1 c are removed in step S15, the respectiveetching rates of the sidewall spacer SW1 c and the insulating film IL6are preferably adjusted to satisfy the following relationships: T2 a≦T2c−3 nm, and T2 b≦T2 c−3 nm. That is, until the entire sidewall spacersSW1 c are removed after starting of the etching back process in stepS15, each of the insulating films IL6 located over the sidewalls of thegate electrodes GE1 and GE2 preferably has its thickness decreased by 3nm or more due to the side etching. This arrangement can make the widthsT1 a and T1 b of the sidewall spacers SW2 a and SW2 b smaller than thewidth T1 c of the sidewall spacer SW2 c, and can appropriately ensurethe difference between the widths (specifically, difference between thewidth T1 c and each of the widths T1 a and T1 b). FIG. 21 shows thethicknesses T2 a, T2 b, and T2 c of the insulating films IL6 over thesidewalls of the gate electrodes GE1, GE2, and GE3.

The thickness T2 a of the insulating film IL6 over the sidewall of thegate electrode GE1 corresponds to the thickness (size) of the insulatingfilm IL6 over the sidewall of the gate electrode GE1 as measured in thedirection parallel to the gate length direction of the gate electrodeGE1. The measurement direction of the thickness T2 a of the insulatingfilm IL6 is the same as that of the width T1 a of the sidewall spacerSW2 a. The thickness T2 b of the insulating film IL6 over the sidewallof the gate electrode GE2 corresponds to the thickness (size) of theinsulating film IL6 over the sidewall of the gate electrode GE2 asmeasured in the direction parallel to the gate length direction of thegate electrode GE2. The measurement direction of the thickness T2 b ofthe insulating film IL6 is the same as that of the width T1 b of thesidewall spacer SW2 b. The thickness T2 c of the insulating film IL6over the sidewall of the gate electrode GE3 corresponds to the thickness(size) of the insulating film IL6 over the sidewall of the gateelectrode GE3 as measured in the direction parallel to the gate lengthdirection of the gate electrode GE3. The measurement direction of thethickness T2 c of the insulating film IL6 is the same as that of thewidth T1 c of the sidewall spacer SW2 c.

As mentioned above, in the stage where the entire sidewall spacer SW1 cis removed, the relationships of T1 a≦T2 c−3 nm and T2 b≦T2 c−3 nm aresatisfied, so that at the end of the step S15, each of the thickness T1a of the sidewall spacer SW2 a, and the width T1 b of the sidewallspacer SW2 b can be smaller than the width T1 c of the sidewall spacerSW2 c by 3 nm or more. That is, the following relationships can besatisfied: T1 a≦T1 c−3 nm, and T1 b≦T1 c−3 nm. Thus, each of the widthT1 a and T1 b of the sidewall spacers SW2 a and SW2 b can be set smallerthan the width T1 c of the sidewall spacer SW2 c, which can accuratelyensure the difference therebetween (namely, difference between the widthT1 c and each of the widths T1 a and T1 b). Even when the semiconductordevices have production tolerances, the widths T1 a and T1 b of thesidewall spacers SW2 a and SW2 b can be surely maintained to be smallerthan the width T1 c of the sidewall spacer SW2 c (that is, T1 a<T1 c,and T1 b<T1 c).

When the thickness of the insulating film. IL7 formed in step S12 isexcessively great, the width (corresponding to the size in the directionparallel to the gate length direction) of the sidewall spacer SW1 formedin step S13 becomes larger, which increases the amount of etching of thesidewall spacer SW1 c in step S15. In this case, variations in width (T1a, T1 b, T1 c) of the sidewall spacers SW2 a, SW2 b, and SW2 c finallyformed might be created. This is because as an insulating film becomesthicker, variations (fluctuations) in thickness of the insulating filmtends to be generated. The large thickness of the formed insulating filmIL7 leads to variations in width of the sidewall spacer SW1, whichresults in variations in width (T1 a, T1 b, T1 c) of the sidewallspacers SW2 a, SW2 b, and SW2 c finally formed. As the film to be etchedbecomes thicker, unevenness in etching might occur upon etching. Whenthe thickness of the formed insulating film IL7 is excessively thick tomake the width of the sidewall spacer SW1 much larger, the unevenness inetching tends to cause variations in width (T1 a, T1 b, T1 c) of thesidewall spacers SW2 a, SW2 b, and SW2 c finally formed.

For this reason, the formation thickness (thickness) T4 of theinsulating film IL7 formed in step S12 is preferably smaller (thinner)than the formation thickness (thickness) T3 of the insulating film IL6formed in step S11 (that is, T4<T3). Thus, variations in width (T1 a, T1b, T1 c) of the sidewall spacers SW2 a, SW2 b, and SW2 c can besuppressed or prevented.

The etching back process of the sidewall spacer SW1 c and the insulatingfilm IL6 is more preferably performed on the etching conditions in whichthe formation thickness T4 of the insulating film IL7 is smaller thanthe formation thickness T3 of the insulating film IL6 (T4<T3) and theetching rate of the insulating film IL6 is larger (faster) than that ofthe sidewall spacer SW1 c (insulating film IL7) in step S15. Thus, evenwhen the width of the sidewall spacer SW1 c becomes small because of thethin formation thickness T4 of the insulating film IL7, in step S15, thethickness of the insulating film IL6 over each sidewall of the gateelectrodes GE1 and GE2 can be sufficiently reduced during the etchingprocess of the sidewall spacers SW1 c. This can increase the differencebetween the width T1 c of the sidewall spacer SW2 c formed in step S15and each of the widths T1 a and T1 b of the sidewall spacers SW2 a andSW2 b.

In ion-implanting in the semiconductor substrate with the insulatingfilm formed thereover, the ease of penetration of impurities differsdepending on the material of the insulating film. The silicon nitridefilm is less likely to allow impurities for ion implantation (forexample, phosphorus (P), boron (B), or arsenic (As)) to penetrate thesubstrate than the silicon oxide film. Thus, when the sidewall spacerformed over the sidewall of the gate electrode is formed of a laminationof a silicon nitride film and a silicon oxide film, implanted impurityions nonuniformly penetrate the sidewall spacer in the ion implantationfor forming the source and drain regions. As a result, the impurity ionsmight be nonuniformly implanted into regions directly under the sidewallspacers of the semiconductor substrate. This leads to nonuniformconcentration of impurities in the extension region directly under thesidewall spacer, causing variations (fluctuations) in state (impuritydistribution) of the extension regions between the MISFETs, which mightresult in variations (fluctuations) in characteristics of the MISFET.

In contrast, in this embodiment, each of the sidewall spacers SW2 a, SW2b, and SW2 c is formed of the insulating film IL6. That is, the sidewallspacers SW2 a, SW2 b, and SW2 c each are formed of the single insulatingfilm. This structure can prevent the implanted impurity ions fromnonuniformly penetrating the sidewall spacers (SW2 a, SW2 b, SW2 c) inthe ion implantation for forming the source and drain regions in stepS16, and can also prevent the impurity ions from being nonuniformlyimplanted into the region directly under the sidewall spacers (SW2 a,SW2 b, SW2 c) of the semiconductor substrate SUB. Thus, this embodimentcan suppress or prevent variations (fluctuations) in state (impuritydistribution) of the extension regions between the MISFETs, and thus canalso suppress and prevent variations (fluctuations) in characteristicsbetween the MISFETs. Therefore, this embodiment can improve theperformance of the semiconductor device. Further, this embodiment canalso improve the reliability of the semiconductor device.

For example, when the insulating film IL6 is formed of a single siliconoxide film, the sidewall spacers SW2 a, SW2 b, and SW2 c are formed ofthe silicon oxide film. In this case, upon ion-implanting for formingthe source and drain regions in step S16, the implanted impurity ionscan penetrate the sidewall spacers (SW2 a, SW2 b, SW2 c) formed of thesingle layer to some degree. However, the ease of penetration of the ionimpurities tends to be uniform because the entire sidewall spacers (SW2a, SW2 b, SW2 c) are formed of the single silicon oxide film. As aresult, the impurity ions can be uniformly implanted into the regionsdirectly under the sidewall spacers (SW2 a, SW2 b, SW2 c) of thesemiconductor substrate SUB in the ion implantation for forming thesource and drain regions in step S16. Thus, this embodiment can moreaccurately suppress or prevent variations (fluctuations) in state(impurity distribution) of the extension regions between the MISFETs,and thus can also more accurately suppress or prevent variations(fluctuations) in characteristics between the MISFETs.

For example, when the insulating film IL6 is formed of a single nitridefilm, the sidewall spacers SW2 a, SW2 b, and SW2 c are formed of thesilicon nitride film. In this case, upon ion-implanting for forming thesource and drain regions in step S16, the implanted impurity ions areless likely to penetrate the sidewall spacers (SW2 a, SW2 b, SW2 c) eachmade of the single silicon nitride film. Thus, impurity ions hardly beimplanted into the regions directly under the sidewall spacers (SW2 a,SW2 b, SW2 c) of the semiconductor substrate SUB upon ion implanting forformation of the source and drain regions in step S16. Thus, thisembodiment can suppress or prevent variations (fluctuations) in state(impurity distribution) of the extension regions between the MISFETs,and thus can also suppress and prevent variations (fluctuations) incharacteristics between the MISFETs.

The insulating film IL6 is more preferably formed of the single siliconnitride film. In this case, upon ion-implanting for forming the sourceand drain regions in step S16, the impurity ions for implantation can besurely prevented from being implanted into the regions of thesemiconductor substrate SUB directly under the sidewall spacers (SW2 a,SW2 b, SW2 c). Thus, this embodiment can suppress or prevent variations(fluctuations) in state (impurity distribution) of the extension regionsbetween the MISFETs, and thus can also suppress and prevent variations(fluctuations) in characteristics between the MISFETs.

Second Embodiment

In the above first embodiment, each of the widths T1 a and T1 b of thesidewall spacers SW2 a and SW2 b formed in the low and high breakdownvoltage MISFET formation regions 1A and 1B is made smaller than thewidth T1 c of the sidewall spacer SW2 c formed in the high breakdownvoltage MISFET formation region 1C (that is, T1 a<T1 c, and T1 b<T1 c).Further, the width T1 a of the sidewall spacer SW2 a is substantiallyequal to the width T1 b of the sidewall spacer SW2 b (T1 a=T1 b).

In contrast, in a second embodiment, the width T1 b of the sidewallspacer SW2 b formed in the intermediate breakdown voltage MISFETformation region 1B is smaller than the width T1 c of the sidewallspacer SW2 c formed in the high as an etching mask breakdown voltageMISFET formation region 1C (T1 b<T1 c). Further, the width T1 a of thesidewall spacer SW2 a formed in the low breakdown voltage MISFETformation region 1A is smaller than the width T1 b of the sidewallspacer SW2 b formed in the intermediate breakdown voltage MISFETformation region 1B (T1 a<T1 b).

A manufacturing procedure of a semiconductor device in the secondembodiment of the invention will be described below with reference tothe accompanying drawings. FIG. 38 shows another flowchart ofmanufacturing steps of the semiconductor device in the secondembodiment. FIGS. 39 to 45 are cross-sectional views of main parts ofother manufacturing steps of the semiconductor device in the secondembodiment. FIG. 38 corresponds to FIG. 2, showing the flowchartfollowing the flowchart (steps S1 to S10) shown in FIG. 1.

The manufacturing procedure of the second embodiment differs from thatof the first embodiment mainly in that steps S21, S22, and S23 shown inFIG. 38 are added after the above step S14 (removal of the sidewallspacers SW1 a and SW1 b) and before the above step S15 (formation of thesidewall spacer SW2 by etching back). The differences will bespecifically described below.

The manufacturing procedure of the second embodiment is substantiallythe same as that of the first embodiment until the structure shown inFIG. 20 is obtained. Thus, the repeated description thereof will beomitted, and the steps after obtaining the structure shown in FIG. 20will be described below.

In this embodiment, like the first embodiment, after the above step S14is performed to obtain the structure shown in FIG. 20, as shown in FIG.39, an insulating film IL10 is formed over the main surface of thesemiconductor substrate SUB, specifically, over the insulating film IL6to cover the sidewall spacers SW1 c (in step S21 shown in FIG. 38).

The insulating film IL10 is an insulating film for controlling the widthof the sidewall spacer SW2 to be formed later over the sidewalls of thegate electrodes GE1, GE2, and GE3. The insulating film IL10 ispreferably a single layer of an insulating film, and made of materialdifferent from the insulating film IL6. The insulating film IL10 ispreferably formed of the same material as that of the insulating filmIL7. That is, when the insulating film IL7 is a silicon nitride film,the insulating film IL10 is also preferably a silicon nitride film. Whenthe insulating film IL7 is a silicon oxide film, the insulating filmIL10 is also preferably a silicon oxide film. The insulating film IL10can be formed, for example, using the CVD method or the like. Theformation thickness T5 of the insulating film IL10 formed in step S21 ispreferably smaller (thinner) than the formation thickness T3 of theinsulating film IL6 formed in step S11. The formation thickness T5 ofthe insulating film IL10 is set taking into consideration a differencebetween the width (T1 b) of the sidewall spacer SW2 b and the width (T1a) of the sidewall spacer SW2 a to be formed later.

Then, as shown in FIG. 40, the insulating film IL10 is subjected toetching back (etching, dry etching, anisotropic etching) by theanisotropic etching technique to thereby form sidewall spacers(sidewalls, sidewall insulating films) SW3 as the sidewall insulatingfilm over the side surfaces (sidewalls) IL6 a of the insulating film IL6(in step S22 shown in FIG. 38).

In step S22, a part of the insulating film. IL10 located over each sidesurface IL6 a of the insulating film IL6 is left as the sidewall spacerSW3, and the remaining part of the insulating film IL10 in the otherregion is removed. Thus, after the step S22, the insulating film IL10locally remaining over each side surface IL6 a of the insulating filmIL6 serves as the sidewall spacer SW3, so that the insulating film IL6except for those covered by the sidewall spacers SW3 and SW1 c isexposed.

The sidewall spacer SW3 formed over the side surface IL6 a of theinsulating film IL6 corresponding to the sidewall of the gate electrodeGE1 in the low breakdown voltage MISFET formation region 1A ishereinafter referred to as a “sidewall spacer SW3 a”. The sidewallspacer SW3 formed over the side surface IL6 a of the insulating film IL6corresponding to the sidewall of the gate electrode GE2 in theintermediate breakdown voltage MISFET formation region 1B is hereinafterreferred to as a “sidewall spacer SW3 b”. The sidewall spacer SW3 formedover the side surface IL6 a of the insulating film IL6 corresponding tothe sidewall of the gate electrode GE3 in the high breakdown voltageMISFET formation region 1C is hereinafter referred to as a “sidewallspacer SW3 c”.

In the high breakdown voltage MISFET formation region 1C, the sidewallspacers SW1 c remain, so that the sidewall spacers SW3 c are formed overthe side surfaces IL6 a of the insulating films IL6 via the respectivesidewall spacers SW1 c. In contrast, in the low breakdown voltage MISFETformation region 1A and the intermediate breakdown voltage MISFETformation region 1B, the sidewall spacers SW1 a and SW1 b are removed instep S14, so that the sidewall spacers SW3 a and SW3 b are formeddirectly over the respective side surfaces IL6 a of the insulating filmsIL6.

That is, after the process in step S22, in the high breakdown voltageMISFET formation region 1C, a lamination of the sidewall spacer SW1 cand the sidewall spacer SW3 c is formed over the side surface IL6 a ofthe insulating film IL6 corresponding to each sidewall of the gateelectrode GE3. In the intermediate breakdown voltage MISFET formationregion 1B, the sidewall spacer SW3 b is formed over the side surface IL6a of the insulating film IL6 corresponding to each sidewall of the gateelectrode GE2. In the low breakdown voltage MISFET formation region 1A,the sidewall spacer SW3 a is formed over the side surface IL6 a of theinsulating film. IL6 corresponding to each sidewall of the gateelectrode GE1.

The insulating film IL10 is preferably formed of the same kind ofmaterial as that of the insulating film IL7. In such a case, thesidewall spacer SW1 c and the sidewall spacer SW3 c are formed of thesame kind of material. Thus, the sidewall spacer SW1 c cannot beobviously distinguished from the sidewall spacer SW3 c. The sidewallspacer including the integration of the sidewall spacer SW1 c and thesidewall spacer SW3 c can also be formed over the side surface IL6 a ofthe insulating film IL6 corresponding to each sidewall of the gateelectrode GE3 in the high breakdown voltage MISFET formation region 1C.

In step S22, the etching back is preferably performed under conditions(etching conditions) that make an etching rate of the insulating filmIL10 larger (higher) than that of the insulating film IL6. In otherwords, in step S22, the etching back is preferably performed underconditions (etching conditions) that make an etching rate of theinsulating film IL6 smaller (lower) than that of the insulating filmIL10. That is, in step S22, the etching back is preferably performed onthe etching conditions in which the insulating film IL6 is less likelyto be etched than the insulating film IL10. Thus, in step S22, theinsulating film IL6 can serve as an etching stopper. In step S22, theinsulating film IL6 can be suppressed or prevented from being etched.

In step S22, the etching rates of the insulating film IL6 and theinsulating film. IL10 need to differ from each other. Also in step S23to be described later, the etching rate of the insulating film IL6 needsto be different from that of the insulating film IL10 (sidewall spacerSW3). Thus, the insulating film IL6 and the insulating film IL10 areformed of different materials.

Taking into consideration the etching back process of the sidewallspacers SW3 b and SW3 c and the sidewall spacers SW1 c in step S15 to bedescribed later, the insulating film IL7 and the insulating film IL10are preferably formed of the same material such that the sidewall spacerSW3 and the sidewall spacer SW1 c are formed of the same material. Whenthe insulating film IL7 and the insulating film IL10 are formed of thesame material, the etching conditions for the etching back process ofthe insulating film IL10 in step S22 can be substantially the same asthose of the etching back process of the insulating film IL7 in stepS13.

In step S22 and step S23 to be described later, the etching conditionsare preferably adopted which can etch the insulating film IL10 and whichsuppresses etching of the insulating film IL6 as much as possible. Thus,the material of the insulating film IL10 is preferably selected that canhave a high etching selectivity as compared to the material of theinsulating film IL6. From this point, preferably, one of the insulatingfilm IL6 and the insulating film IL10 is formed of a silicon oxide film,whereas the other of the insulating film IL6 and the insulating filmIL10 is formed of a silicon nitride film.

Then, the sidewall spacers SW3 (that is, sidewall spacers SW3 a) in thelow breakdown voltage MISFET formation region 1A are removed, and thesidewall spacers SW3 (that is, sidewall spacers SW3 b and SW3 c)

in the intermediate and high breakdown voltage MISFET formation regions1B and 1C are maintained (in step S23 shown in FIG. 38).

The process in step S23 can be performed in the following way. That is,as shown in FIG. 41, first, a photoresist layer (mask layer) PR11 isformed over the semiconductor substrate SUB to cover the low breakdownvoltage MISFET formation region 1B and the high breakdown voltage MISFETformation region 1C, and to expose the low breakdown voltage MISFETformation region 1A. Then, the sidewall spacers SW3 (that is, sidewallspacers SW3 a) formed in the low breakdown voltage MISFET formationregion 1A are removed by etching. Thereafter, as shown in FIG. 42, thephotoresist layer PR11 is removed. In this way, the process in step S23is performed to remove the sidewall spacers SW3 a in the low breakdownvoltage MISFET formation region 1A.

In the step S23, the etching is performed with the sidewall spacers SW3(SW3 a) in the low breakdown voltage MISFET formation region 1A exposed,and the sidewall spacers SW3 (SW3 b, SW3 c) in the intermediate and highbreakdown voltage MISFET formation regions 1B and 1C not exposed (thatis, covered with the photoresist layer PR11). In the etching process instep S23, the sidewall spacers SW3 (SW3 a) in the low breakdown voltageMISFET formation region 1A are removed, whereas the sidewall spacers SW3(SW3 b, SW3 c) in the intermediate and high breakdown voltage MISFETformation regions 1B and 1C remain without being removed.

In step S23, the etching is preferably performed under conditions(etching conditions) that make an etching rate of the sidewall spacerSW3 larger (higher) than that of the insulating film IL6. In otherwords, in step S23, the etching is preferably performed under conditions(etching conditions) that make an etching rate of the insulating filmIL6 smaller (lower) than that of the sidewall spacer SW13. That is, instep S23, the etching is preferably performed on the etching conditionsin which the insulating film IL6 is less likely to be etched than thesidewall spacer SW3. In step S23, the insulating film IL6 can besuppressed or prevented from being etched.

In step S23, the sidewall spacers SW3 a are desirably removed whilesuppressing the etching of the insulating film IL6 as much as possible.Thus, the thickness of the insulating film IL6 in the low breakdownvoltage MISFET formation region 1A can be suppressed or prevented frombeing reduced due to the etching in step S23. As a result, thisembodiment can suppress or prevent a difference in thickness of theinsulating film IL6 among the low, intermediate, and high breakdownvoltage MISFET formation regions 1A, 1B, and 1C. From this point, theetching in step S23 is preferably wet etching, which can suppress theetching of the insulating film IL6 as much as possible, whileappropriately removing the sidewall spacers SW3 a. The application ofthe wet etching to the silicon oxide film and the silicon nitride filmcan easily achieve the high etching selectivity. More preferably, one ofthe insulating films IL6 and IL10 is the silicon oxide film, the otheris the silicon nitride film, and the etching in step S23 is preferablythe wet etching. For example, when the insulating film IL6 is thesilicon nitride film, and the insulating film IL10 is the silicon oxidefilm, in step S23, the wet etching using hydrofluoric acid (bufferedhydrofluoric acid) can be suitably used.

In step S22, anisotropic etching is necessary. Thus, dry etching isperformed. Since in step S23, the sidewall spacers SW3 a are removedwhile suppressing the etching of the exposed insulating film IL6,isotropic etching is preferable, and wet etching is more preferable.

The steps described above produce the structure shown in FIG. 42. Thatis, in the high breakdown voltage MISFET formation region 1C, alamination of the sidewall spacer SW1 c and the sidewall spacer SW3 c isformed over the side surface IL6 a of the insulating film IL6corresponding to each sidewall of the gate electrode GE3. In theintermediate breakdown voltage MISFET formation region 1B, the sidewallspacers SW3 b are formed over the side surfaces IL6 a of the insulatingfilms IL6 corresponding to the sidewalls of the gate electrode GE2. Thewidth T6 c of the sidewall spacer SW3 c is substantially the same as thewidth T6 b of the sidewall spacers SW3 b (T6 b=T6 c). In the lowbreakdown voltage MISFET formation region 1A, the side surfaces IL6 a ofthe insulating films IL6 corresponding to the sidewalls of the gateelectrode GE1 are exposed (that is, with no sidewall spacer formed overthe side surface IL6 a).

The width T6 b of the sidewall spacer SW3 b corresponds to a distance(distance measured in the direction parallel to the gate lengthdirection of the gate electrode GE2) between the side surface (sidesurface of the sidewall spacer SW3 b) of the sidewall spacer SW3 bopposed (adjacent) to the side surface IL6 a of the insulating film IL6,and a side surface (side surface of the sidewall spacer SW3 b) oppositeto the above side surface, among the side surfaces of the sidewallspacer SW3 b. The width T6 c of the sidewall spacer SW3 c corresponds toa distance (distance measured in the direction parallel to the gatelength direction of the gate electrode GE3) between the side surface(side surface of the sidewall spacer SW3 c) of the sidewall spacer SW3 copposed (adjacent) to the side surface IL6 a of the insulating film IL6,and a side surface (side surface of the sidewall spacer SW3 c) oppositeto the above side surface, among the side surfaces of the sidewallspacer SW3 c. The width of each of the sidewall spacers SW3 b and SW3 ccan be regarded as the thickness of each of the sidewall spacers SW3 band SW3 c (thickness of a part located over the sidewall IL6 a of theinsulating film IL6).

The following steps are basically the same as those of the firstembodiment. That is, as shown in FIGS. 43 and 44, the sidewall spacersSW3 b, SW3 c, and SW1 c and the insulating film IL6 are subjected toetching back (etching, dry etching) to thereby form the sidewall spacerSW2 as the sidewall insulating film over each sidewall of the gateelectrodes GE1, GE2, and GE3 (in step S15 shown in FIG. 38).

The etching conditions in the etching back process of step S15 aresubstantially the same as those of the first embodiment.

In step S15, the sidewall spacers SW3 b, SW3 c, and SW1 c are removed,and the insulating film IL6 mains over each sidewall of the gateelectrodes GE1, GE2, and GE3 to become the sidewall spacer SW2 with theinsulating film IL6 in the remaining regions removed. In this way, theinsulating films IL6 remaining over the sidewalls of the gate electrodesGE1, GE2, and GE3 form the sidewall spacers SW2. In step S15, theinsulating films IL6 except for the parts of the insulating film IL6remaining as the sidewall spacer SW2 over the sidewalls of the gateelectrodes GE1, GE2, and GE3 are removed as a whole.

In step S15, the whole sidewall spacers SW3 b, SW3 c, and SW1 c arepreferably removed not to be left over. Thus, after the end of step S15,the sidewall spacers SW2 are formed of the insulating film IL6 remainingover the sidewalls of the gate electrodes GE1, GE2, and GE3, but thesidewall spacer SW1 is not formed (does not remain). That is, after theend of step S15, the sidewall spacer SW2 formed over each sidewall ofthe gate electrodes GE1, GE2, and GE3 is formed not of both theinsulating film IL6 and remaining parts of the sidewall spacers SW1 andSW3, but of the single layer of the insulating film IL6.

FIG. 43 corresponds to FIG. 21 described above, and shows the halfwaystage of the etching process in step S15. Specifically, FIG. 43 showsthe stage directly after removal of the entire sidewall spacers SW3 b,SW3 c, and SW1 c during the etching process in step S15. FIG. 44corresponds to FIG. 21 described above, and shows the stage directlyafter the end of the etching process in step S15 continued after thestage of FIG. 43.

In the etching process of step S15, in the stage where the entiresidewall spacers SW3 b, SW3 c, and SW1 c are removed, the insulatingfilm IL6 preferably remains over the semiconductor substrate SUB in theform of layer as shown in FIG. 43. The reason for this is the same asthat in the first embodiment. After removing the entire sidewall spacersSW3 b, SW3 c, and SW1 c in the etching process of step S15, etching ispreferably continued not to leave the insulating film IL6 in the form oflayer over the semiconductor substrate SUB. That is, the insulatingfilms IL6 except for the parts thereof serving as the sidewall spacersSW2 are removed.

When the offset spacers SP are formed over the sidewalls of the gateelectrodes GE1, GE2, and GE3, the sidewall spacer SW2 is formed overeach sidewall of the gate electrodes GE1, GE2, and GE3 via the offsetspacer SP.

In the second embodiment, the width T1 c of the sidewall spacer SW2 cformed over the sidewall of the gate electrode GE3 is larger than thewidth T1 b of the sidewall spacer SW2 b formed over the sidewall of thegate electrode GE2 (T1 c>T1 b). The width T1 b of the sidewall spacerSW2 b formed over the sidewall of the gate electrode GE2 is larger thanthe width T1 a of the sidewall spacer SW2 a formed over the sidewall ofthe gate electrode GE1 (T1 b>T1 a). In other words, the width T1 a ofthe sidewall spacer SW2 a is smaller than the width T1 b of the sidewallspacer SW2 b (T1 a<T1 b), and the width T1 b of the sidewall spacer SW2b is smaller than the width T1 c of the sidewall spacer SW2 c (that is,T1 b<T1 c).

As mentioned above, in the first embodiment, the width T1 a of thesidewall spacer SW2 a is substantially the same as the width T1 b of thesidewall spacer SW2 b (T1 a=T1 b). In the second embodiment, the widthT1 a of the sidewall spacer SW2 a is smaller than the width T1 b of thesidewall spacer SW2 b (T1 a<T1 b).

In the second embodiment, the widths T1 a, T1 b, and T1 c of thesidewall spacers SW2 a, SW2 b, and SW2 c have the following relationshipof T1 a<T1 b<T1 c. The reason for this will be described below.

In the etching process of step S15, not only the anisotropic etching,but also side etching is also performed. Since in the high breakdownvoltage MISFET formation region 1C, the sidewall spacers SW3 c and SW1 care formed over the side surfaces IL6 a of the insulating films IL6.Until the entire sidewall spacers SW3 c and SW1 c are removed, the sidesurface IL6 a of the insulating film IL6 is not subjected to the sideetching. That is, in the high breakdown voltage MISFET formation region1C, only after the removal of the sidewall spacers SW3 c and SW1 c andexposure of the side surface IL6 a of the insulating film IL6, the sidesurface IL6 a of the insulating film IL6 is subjected to side etchingduring the entire etching time in step S15.

In the intermediate breakdown voltage MISFET formation region 1B, thesidewall spacer SW3 b is formed over each side surface IL6 a of theinsulating film. IL6. Until the entire sidewall spacer SW3 b is removed,the side surface IL6 a of the insulating film IL is not subjected to theside etching. That is, in the intermediate breakdown voltage MISFETformation region 1B, only after the removal of the sidewall spacer SW3 band exposure of the side surface IL6 a of the insulating film IL6,

the side surface IL6 a of the insulating film IL6 is subjected to theside etching in the whole etching time in step S15.

The width T6 b of the sidewall spacer SW3 b is substantially the same asthe width T6 c of the sidewall spacer SW3 c. Thus, the sum of the widthsof the sidewall spacer SW3 c and sidewall spacer SW1 c (thickness overthe side surface IL6 a) is more than the width of the sidewall spacerSW3 b (thickness over the side surface IL6 a) by the sidewall spacer SW1c. The time required to remove the sidewall spacers SW3 c and SW1 c inthe high breakdown voltage MISFET formation region 1C to expose the sidesurface IL6 a of the insulating film IL6 is longer than that required toremove the sidewall spacer SW3 b in the intermediate breakdown voltageMISFET formation region 1B and to expose the side surface IL6 a of theinsulating film IL6 by the time required for etching the sidewall spacerSW1 c.

In contrast, in the low breakdown voltage MISFET formation region 1A,the etching in step S15 is started without the sidewall spacers formedover the side surfaces IL6 a of the insulating film IL6 (with thesidewall spacer SW3 a already removed). Thus, in the low breakdownvoltage MISFET formation region 1A, the side surfaces IL6 a of theinsulating films IL6 are subjected to side etching during the whole timeof the etching in step S15.

The time during which the side surface IL6 a of the insulating film IL6is subjected to side etching in the intermediate breakdown voltageMISFFET formation region 1B becomes longer than that in the highbreakdown voltage MISFET formation region 1C. The time during which theside surface IL6 a of the insulating film IL6 is subjected to sideetching in the low breakdown voltage MISFFET formation region 1A becomeslonger than that in the intermediate breakdown voltage MISFET formationregion 1B. When the side surface IL6 a of the insulating film IL6 issubjected to side etching, the longer the side etching time, the largerthe amount of side etching (thickness of the side-etched part) becomes,which decreases the thickness of the insulating film IL6 over thesidewall of the gate electrode.

As a result, in the stage after the end of the etching in step S15, thethickness of the insulating film IL6 remaining over the sidewalls of thegate electrode GE2 in the intermediate breakdown voltage MISFETformation region 1B becomes smaller (thinner) than that of theinsulating film IL6 remaining over the sidewalls of the gate electrodeGE3 in the high breakdown voltage MISFET formation region 1C. Then, inthe stage after the end of the etching in step S15, the thickness of theinsulating film IL6 remaining over the sidewall of the gate electrodeGE1 in the low breakdown voltage MISFET formation region 1A becomessmaller (thinner) than that of the insulating film IL6 remaining overthe sidewall of the gate electrode GE2 in the intermediate breakdownvoltage MISFET formation region 1B. Further, the width T1 b of thesidewall spacer SW2 b is smaller than the width T1 c of the sidewallspacer SW2 c, and the width T1 a of the sidewall spacer SW2 a is smallerthan the width T1 b of the sidewall spacer SW2 c (T1 a<T1 b<T1 c).

As mentioned above, in the second embodiment, in the high breakdownvoltage MISFET formation region 1C, the sidewall spacers SW3 c and SW1 care left over the sidewalls IL6 a of the insulating films IL6.

In the intermediate breakdown voltage MISFET formation region 1B, thesidewall spacer SW3 b is left over each sidewall IL6 a of the insulatingfilm IL6. In the low breakdown voltage MISFET formation regions 1A, theetching back process in step S15 is performed with the side surface IL6a of the insulating film IL6 exposed. In the high breakdown voltageMISFET formation region 1C, the sidewall spacer SW3 c and the sidewallspacer SW1 c can serve as a prevention film of side etching of theinsulating film IL6. The side etching time of the insulating film IL6 inthe high breakdown voltage MISFET formation region 1C can be shortenedto decrease the amount of side etching of the insulating film IL6 ascompared to in the low and intermediate breakdown voltage MISFETformation regions 1A and 1B. In the intermediate breakdown voltageMISFET formation region 1B, the sidewall spacer SW3 b can serve as aprevention film of side etching of the insulating film IL6. The sideetching time of the insulating film IL6 in the intermediate breakdownvoltage MISFET formation region 1B can be shortened to decrease theamount of side etching of the insulating film IL6 as compared to in thelow breakdown voltage MISFET formation region 1A. Due to such adifference in amount of the side etching of the insulating film IL6between the MISFET formation regions, the thickness of the insulatingfilm IL6 over the sidewall of the gate electrode is thinned in the high,intermediate, and low breakdown voltage MISFET formation regions 1C, 1B,and 1A in that order, so that the widths T1 a, T1 b, and T1 c of thesidewall spacers SW2 a, SW2 b, and SW2 c can have the relationship of T1a<T1 b<T1 c.

In this way, the sidewall spacers SW2 (SW2 a, SW2 b, SW2 c) are formed.

Then, as shown in FIG. 45, the source and drain regions SD1, SD2, andSD3 which are n⁺-type semiconductor regions (n-type impurity diffusionlayer) are formed (in step S16 shown in FIG. 38). The process in stepS16 is the same as that in the first embodiment, and the repeateddescription thereof will be omitted below.

The annealing process (heat treatment) is performed to activate theprocess in step S17. The metal silicide layer MS is formed in a silicideprocess in step S18. Then, the above insulating film IL8, the contactholes CT, the plugs PG, the insulating film IL9, and the wirings M1 canbe formed in the same way as the first embodiment. The illustration anddescription thereof will be omitted.

In the way described above, the semiconductor device of the secondembodiment is manufactured.

In the first embodiment, the width T1 a of the sidewall spacer SW2 aformed over the sidewall of the gate electrode GE1 and the width T1 b ofthe sidewall spacer SW2 b formed over the sidewall of the gate electrodeGE2 are smaller than the width T1 c of the sidewall spacer SW2 c formedover the sidewall of the gate electrode GE3. The width T1 a of thesidewall spacer SW2 a formed over the sidewall of the gate electrode GE1is substantially the same as the width T1 b of the sidewall spacer SW2 bformed over the sidewall of the gate electrode GE2. That is, T1 a=T1b<T1 c

In contrast, in the second embodiment, the width T1 a of the sidewallspacer SW2 a formed over the sidewall of the gate electrode GE1 issmaller than the width T1 b of the sidewall spacer SW2 b formed over thesidewall of the gate electrode GE2. The width T1 b of the sidewallspacer SW2 b is smaller than the width T1 c of the sidewall spacer SW2 cformed over the sidewall of the gate electrode GE3. That is, T1 a<T1b<T1 c.

Reflecting the relationship of T1 a<T1 b<T1 c, the distance (distance inparallel to the gate length direction) between the source/drain regionSD1 and the channel formation region in the MISFETQ1 can be smaller thanthe distance (distance in the direction parallel to the gate lengthdirection) between the source/drain region SD2 and the channel formationregion in the MISFETQ2. The distance (distance in parallel to the gatelength direction) between the source/drain region SD2 and the channelformation region in the MISFETQ2 can be smaller than the distance(distance in the direction parallel to the gate length direction)between the source/drain region SD3 and the channel formation region inthe MISFETQ3.

Thus, the size (specifically, the size in the gate length direction) ofthe extension region EX1 having a low impurity concentration andextending between the source/drain region SD1 and the channel formationregion in the MISFETQ1 can be smaller than that (specifically, thedistance in the gate length direction) of the extension region EX2having a low impurity concentration and extending between thesource/drain region SD2 and the channel formation region in theMISFETQ2. Thus, the size (specifically, the size in the gate lengthdirection) of the extension region EX2 having a low impurityconcentration and extending between the source/drain region SD2 and thechannel formation region in the MISFETQ2 can be smaller than that(specifically, the distance in the gate length direction) of theextension region EX3 having a low impurity concentration and extendingbetween the source/drain region SD3 and the channel formation region inthe MISFETQ3.

Thus, in the MISFETQ3, the distance between the source/drain region SD3and the channel formation region can be increased as compared to theMISFFETQ1 and Q2 to improve the breakdown voltage of the MISFETQ3. Incontrast, in the MISFETQ1, the distance between the source/drain regionSD1 and the channel formation region can be decreased as compared tothose in the MISFETQ2 and Q3 to improve the current driving force of theMISFETQ1. In the MISFETQ2, the distance between the source/drain regionSD2 and the channel formation region can be increased as compared to theMISFFETQ1 to improve the breakdown voltage of the MISFETQ2. In contrast,in the MISFETQ2, the distance between the source/drain region SD2 andthe channel formation region can be decreased as compared to those inthe MISFETQ3 to improve the current driving force of the MISFETQ2. Thisembodiment can improve the total performance of the semiconductordevice.

In other points, the second embodiment can also obtain substantially thesame effects as those of the first embodiment.

In the second embodiment, in step S12, the insulating film IL7 isformed, and then in step S13, the insulating film IL7 is etched back tothereby form the sidewall spacers SW1 a, SW1 b, and SW1 c. In step S21,the insulating film IL10 is formed, and then in step S22, the insulatingfilm IL10 is etched back to thereby form the sidewall spacers SW3 a, SW3b, and SW3 c. Thus, in steps S13 and S22, the amount of overetching ofthe insulating film IL6 is substantially the same among the low,intermediate, and high breakdown voltage MISFET formation regions 1A,1B, and 1C. Thus, directly before the process in step S15, the thicknessof the insulating film IL6 is substantially the same among the low,intermediate, and high breakdown voltage MISFET formation regions 1A,1B, and 1C. The timings of removing the insulating films IL6 except forthose located over the sidewalls of the gate electrodes GE1, GE2, andGE3 in step S15 can be substantially identical to each other. Thus, theetching back process in step S15 can suppress or prevent the excessiveoveretching in either the low, intermediate, or high breakdown voltageMISFET formation regions 1A, 1B, or 1C to suppress or prevent the damageon the semiconductor substrate SUB. This embodiment can suppress orprevent the overetching of the semiconductor substrate SUB in either thelow, intermediate, or high breakdown voltage MISFET formation regions1A, 1B, or 1C to thereby suppress or prevent the damage on thesemiconductor substrate SUB, improving the reliability of thesemiconductor device manufactured.

In the second embodiment, in step S14, the sidewall spacers SW1 a andSW1 b are removed to leave the sidewall spacers SW1 c. Then, in stepS23, the sidewall spacers SW3 a are removed to leave the sidewallspacers SW3 b and SW3 c. Then, in step S15, the sidewall spacers SW1 cand the insulating films IL6 are etched back. Desirably, in the stepsS14 and S23, the sidewall spacers SW1 a and SW1 b (in step S14), or thesidewall spacer SW3 a (in step S23) may be etched and removed, whilesuppressing the etching of the insulating film IL6 as much as possible.This arrangement can more appropriately suppress or prevent thedifference in thickness of the insulating film IL6 among the low,intermediate, and high breakdown voltage formation regions 1A, 1B, and1C directly before the process in step S15. From this point, in stepS14, the etching conditions that sets an etching selectivity of thesidewall spacers SW1 a and SW1 b (insulating film IL7) with respect tothe insulating film IL6 to more than 1 should be preferably selected.The etching selectivity is more preferably 1.5 or more. In step S23, theetching conditions that sets an etching selectivity of the sidewallspacers SW3 a (insulating film IL10) with respect to the insulating filmIL6 to more than 1 should be preferably selected. The etchingselectivity is more preferably 1.5 or more.

Also in the second embodiment, like the first embodiment, as shown inFIG. 43, in the stage where the entire sidewall spacers SW3 b, SW3 c,and SW1 c are removed, the insulating film IL6 preferably remain overthe semiconductor substrate SUB in the form of layer. This arrangementcan surely suppress or prevent the overetching of the semiconductorsubstrate SUB in step S15.

Further, in the second embodiment, as shown in FIG. 43, in step S15, inthe stage where the entire sidewall spacers SW3 b, SW3 c, and SW1 c areremoved, the thickness T2 a of the insulating film IL6 over the sidewallof the gate electrode GE1 is preferably thinner than the thickness T2 bof the insulating film IL6 over the sidewall of the gate electrode GE2by 3 nm or more. The thickness T2 b of the insulating film IL6 over thesidewall of the gate electrode GE2 is preferably thinner than thethickness T2 c of the insulating film IL6 over the sidewall of the gateelectrode GE3 by 3 nm or more. That is, in the stage where the entiresidewall spacers SW3 b, SW3 c, and SW1 c are removed, the flowingrelationships are preferably satisfied: T2 a T2 c−3 nm, and T2 b≦T2 c−3nm. Thus, the thicknesses T1 c, T1 b, and T1 a of the sidewall spacersSW2 a, SW2 b, and SW2 c become smaller in that order, which canaccurately ensure the difference (between the widths T1 c and T1 b, andthe widths T1 b and T1 a).

In the stage where the entire sidewall spacers SW3 b, SW3 c, and SW1 care removed, the relationships of T1 a≦T2 c−3 nm and T2 b≦T2 c−3 nm aresatisfied, so that at the end of the process in step S15, the followingrelationships can be satisfied about the widths T1 a, T1 b, and T1 c ofthe sidewall spacers SW2 a, SW2 b, and SW2 c: T1 a≦T1 b−3 nm, and T1b≦T1 c−3 nm. In other words, the width T1 a of the sidewall spacer SW2 ais smaller than the width T1 b of the sidewall spacer SW2 b by 3 nm ormore, and the width T1 b of the sidewall spacer SW2 b is smaller thanthe width T1 c of the sidewall spacer SW2 c by 3 nm or more. Thus, thewidths T1 c, T1 b, and T1 a of the sidewall spacers SW2 a, SW2 b, andSW2 c become smaller in that order, which can accurately ensure thedifference (between the widths T1 c and T1 b, and the widths T1 b and T1a). Even under the production tolerances, this embodiment can surelymaintain the relationship that the widths T1 c, T1 b, and T1 a of thesidewall spacers SW2 a, SW2 b, and SW2 c become smaller in that order(T1 a<T1 b<T1 c).

The formation thickness (thickness) T4 of the insulating film IL7 formedin step S12 is preferably smaller (thinner) than the formation thicknessT3 of the insulating film IL6 formed in step S11 (that is, T4<T3).Likewise, the formation thickness T5 of the insulating film IL10 formedin step S21 is preferably smaller (thinner) than the formation thickness(thickness) T3 of the insulating film IL6 formed in step S11 (that is,T5<T3). Thus, as mentioned in the first embodiment, this embodiment cansuppress or prevent variations in width (T1 a, T1 b, T1 c) of thesidewall spacers SW2 a, SW2 b, and SW2 c.

The etching back process is preferably performed in step S15 on theetching conditions in which the formation thicknesses T4 and T5 of theinsulating films IL7 and IL10 are smaller than the formation thicknessT3 of the insulating film IL6 and the etching rate of the insulatingfilm IL6 is larger (faster) than that of the sidewall spacers SW3 b, SW3c, and SW1 c (insulating films IL7, IL10). Thus, even when the width ofeach of the sidewall spacers SW3 b, SW3 c, and SW1 c becomes smallbecause of the thin formation thicknesses T4 and T5 of the insulatingfilms IL7 and IL10, in step S15, the thickness of the insulating filmIL6 over each sidewall of the gate electrodes GE1 and GE2 can besufficiently reduced during the etching of the sidewall spacers SW3 b,SW3 c, and SW1 c. This arrangement can increase a difference between thewidth T1 c of the sidewall spacer SW2 c and the width T1 b of thesidewall spacer SW2 b, which spacers are formed in step S15, and canalso increase a difference between the width T1 b of the sidewall spacerSW2 b and the width T1 a of the sidewall spacer SW2 a.

The invention made by the inventors has been specifically describedabove based on the preferred embodiments, and the invention is notlimited to the above embodiments. It is apparent that variousmodifications and changes can be made to those embodiments withoutdeparting the scope of the invention.

For example, in the first and second embodiments, the MISFETQ1 is formedin the low breakdown voltage MISFET formation region 1A, the MISFETQ2 isformed in the intermediate breakdown voltage MISFET formation region 1B,and the MISFETQ3 is formed in the high breakdown voltage MISFETformation region 1C. In the first embodiment, however, either the lowbreakdown voltage MISFET formation region (MISFETQ1) or the intermediatebreakdown voltage MISFET formation region (MISFETQ2) can be omitted. Inthe second embodiment, any one of the low breakdown voltage MISFETformation region 1A (MISFETQ1), the intermediate breakdown voltageMISFET formation region 1B (MISFETQ2), and the high breakdown voltageMISFET formation region 1C (MISFETQ3) can be omitted.

For example, in the first and second embodiments, the width of thesidewall spacer SW2 formed over the sidewall of the gate electrode isset to vary depending on the MISFET having a different breakdownvoltage. In order to vary the width of the sidewall spacer formed overthe sidewall of the gate electrode in each of the MISFETs having thesame breakdown voltage, the methods of the first or second embodimentcan be employed.

Although in the first and second embodiments, the MISFETQ1, Q2, and Q3are the p-channel MISFET, the conduction type of each of the MISFETQ1,Q2, and Q3 can be reversed to form the n-channel MISFET. The MISFETQ1,Q2, and Q3 can be of a mixture of n-channel and p-channel types. Boththe p-channel MISFET and the n-channel MISFET can be formed.

What is claimed is:
 1. A manufacturing method of a semiconductor device,comprising the steps of: (a) providing a semiconductor substrate; (b)forming a first gate electrode via a first gate insulating film and asecond gate electrode via a second gate insulating film over thesemiconductor substrate; (c) forming a first insulating film over thesemiconductor substrate to cover the first gate electrode and the secondgate electrode, the first insulating film having first portions on uppersurfaces of first and second gate electrodes and second portions on sidesurfaces of first and second gate electrodes; (d) forming a firstsidewall insulating film selectively formed on the second portions atthe side surfaces of the second gate electrode; (e) after the step (d),etching back the first sidewall insulating film and the first insulatingfilm to thereby form a second sidewall insulating film with a firstwidth made of the first insulating film, over the side surface of thefirst gate electrode and a third sidewall insulating film with a secondwidth made of the first insulating film, over the side surface of thesecond gate electrode, wherein the first width is smaller than thesecond width.
 2. The manufacturing method of a semiconductor deviceaccording to claim 1, wherein in the step (e), the etching back isperformed not to leave the first sidewall insulating film.
 3. Themanufacturing method of a semiconductor device according to claim 1,wherein in the step (e), the first sidewall insulating film and thefirst insulating film are etched back simultaneously by dry etching. 4.The manufacturing method of a semiconductor device according to claim 1,wherein one of the first insulating film and the first sidewallinsulating film is a silicon oxide film, and the other is a siliconnitride film.
 5. The manufacturing method of a semiconductor deviceaccording to claim 1, wherein in the step (e), in a stage where thefirst sidewall insulating film is removed, the first insulating filmremains over the semiconductor substrate in form of layer.
 6. Themanufacturing method of a semiconductor device according to claim 1,wherein in the step (e), in a stage where the first sidewall insulatingfilm is removed, a surface of the semiconductor substrate is notexposed.
 7. The manufacturing method of a semiconductor device accordingto claim 5, wherein in the step (e), in the stage where the firstsidewall insulating film is removed, a thickness of the first insulatingfilm over the side surface of the first gate electrode is thinner thanthat of the first insulating film over the side surface of the secondgate electrode by 3 nm or more.
 8. The manufacturing method of asemiconductor device according to claim 1, wherein the first width issmaller than the second width by 3 nm or more.
 9. The manufacturingmethod of a semiconductor device according to claim 1, wherein a widthof the first sidewall insulating film formed in the step (d) is smallerthan a thickness of the first insulating film formed in the step (c).10. The manufacturing method of a semiconductor device according toclaim 1, wherein in the step (e), the first sidewall insulating film andthe first insulating film are etched back on etching conditions thatmake an etching rate of the first insulating film higher than that ofthe first sidewall insulating film.
 11. The manufacturing method of asemiconductor device according to claim 1, further comprising a step of:(f) after the step (e), forming a first semiconductor region for asource/drain of a first MISFET with the first gate electrode by ionimplantation into the semiconductor substrate using the first gateelectrode and the second sidewall insulating film as a mask, and forminga second semiconductor region for a source/drain of a second MISFET withthe second gate electrode by ion implantation into the semiconductorsubstrate using the second gate electrode and the third sidewallinsulating film as another mask.
 12. The manufacturing method of asemiconductor device according to claim 11, further comprising a stepof: (b1) after the step (b) and before the step (c), forming a thirdsemiconductor region in the semiconductor substrate by ion implantationinto the semiconductor substrate using the first gate electrode as amask, and forming a fourth semiconductor region by ion implantation intothe semiconductor substrate using the second gate electrode as anothermask, wherein the first semiconductor region and the third semiconductorregion have a same conduction type, and the first semiconductor regionhas a higher impurity concentration than that of the third semiconductorregion, and wherein the second semiconductor region and the fourthsemiconductor region have a same conduction type, and the secondsemiconductor region has a higher impurity concentration than that ofthe fourth semiconductor region.
 13. The manufacturing method of asemiconductor device according to claim 1, wherein the first insulatingfilm is a silicon nitride film, and the first sidewall insulating filmis a silicon oxide film.
 14. The manufacturing method of a semiconductordevice according to claim 1, wherein the second gate insulating film isthicker than the first gate insulating film.
 15. The manufacturingmethod of a semiconductor device according to claim 1, wherein the firstwidth of the second sidewall insulating film corresponds to a size ofthe second sidewall insulating film at a lower part of the side surfaceof the first gate electrode in a direction parallel to a gate lengthdirection of the first gate electrode, and wherein the second width ofthe third sidewall insulating film corresponds to a size of the thirdsidewall insulating film at a lower part of the side surface of thesecond gate electrode in a direction parallel to a gate length directionof the second gate electrode.
 16. The manufacturing method of asemiconductor device according to claim 1, wherein, in the step (e),etching back the first sidewall insulating film and the first insulatingfilm so as to expose upper surfaces of the first gate electrode and thesecond gate electrode and a surface of the semiconductor substrate. 17.The manufacturing method of a semiconductor device according to claim 1,wherein a thickness of the first insulating film which covers the uppersurface and the side surface of the first gate electrode and is etchedin the step (e) is same as that of the first insulating film whichcovers the upper surface and the side surface of the second gateelectrode and is etched in the step (e).
 18. The manufacturing method ofa semiconductor device according to claim 1, wherein, after the step(d), the first sidewall insulating film does not remain only over thesecond portion at the side surface of the first gate electrode.